Bulletin  96 


DEPARTMENT  OF  THE  INTERIOR 


FRANKLIN  K.  LANE,  SECRETARY 

BUREAU  OF  MINES 
VAN.  H.  MANNING,  DIRECTOR 


THE  ANALYSIS  OF  PERMISSIBLE 
EXPLOSIVES 


B    3    115 


BY 


C.  G.  STORM 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICB 
1916 


Bulletin  96 

DEPARTMENT  OF  THE  INTERIOR 

FRANKLIN  K.  LANE,  SECRETARY 

BUREAU  OF  MINES 
VAN.  H.  MANNING.  DIRECTOR 


THE  ANALYSIS  OF  PERMISSIBLE 
EXPLOSIVES 


;  *L*  /*~*A 


BY 


C.  G.  STORM 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1916 


The  Bureau  of  Mines,  in  carrying  out  one  of  the  provisions  of  its  organic 
act — to  disseminate  information  concerning  investigations  made — prints  a 
limited  free  edition  of  each  of  its  publications. 

When  this  edition  is  exhausted,  copies  may  be  obtained  at  cost  price  only 
through  the  Superintendent  of  Documents,  Government  Printing  Office,  Wash- 
ington, D.  C. 

The  Superintendent  of  Documents  is  not  an  official  of  the  Bureau  of  Mines. 
His  is  an  entirely  separate  office,  and  he  should  be  addressed : 
SUPERINTENDENT  OF  DOCUMENTS, 

Government  Printing  Office, 

Washington,  D.  C. 

The  general  law  under  which  publications  are  distributed  prohibits  the  giving 
of  more  than  one  copy  of  a.  publication  to  one  person.  The  price  of  this  publi- 
cation is  15  cents. 


First  edition.    January,  1916. 

ii 


. 


CONTENTS. 

Page. 

Introduction 5 

Acknowledgments 5 

Nature  of  permissible  explosives 6 

Classification  of  permissible  explosives 6 

General  characteristics  of  permissible  explosives 7 

Ammonium  nitrate  explosives 7 

Hydrated  explosives 8 

Organic  nitrate  (other  than  nitroglycerin)  explosives 9 

Nitroglycerin  explosives 9 

Physical  examination  of  permissible  explosives 10 

Determination  of  gravimetric  density 10 

Tests  for  liability  of  exudation ' ! 10 

Tests  for  stability 11 

Abel  test 11 

"  International  "  75°  test 11 

Method  of  making  the  test 11 

Comparison  of  results  of  "  Abel  "  and  "  international "  tests-  12 

Sampling  and  preparation  for  analysis. 12 

Qualitative  analysis 13 

Components  of  low-flame  explosives 13 

Method  of  conducting  qualitative  analysis 14 

Special  qualitative  tests 14 

Test  for  nitropolyglycerin 14 

Test  for  mononitronaphthalene 14 

Test  for  chlorides,  chlorates,  and  perchlorates 14 

Test  for  sugar., '. 15 

Test  for  gum  arable 15 

Test  for  nitrostarch 15 

Test  for  nitrocellulose 15 

Identification  of  wood  pulp  mixed  with  cereal  products 16 

Identification  of  wheat  flour  and  corn  meal 16 

Glycerin  test. 16 

Alkali  test 16 

Mechanical  separation  of  solid  ingredients 17 

Separation  of  ingredients  by  screening 17 

Specific-gravity  separation  of  ingredients 18 

Example  of  usefulness  of  method 20 

Microscopic  examination 20 

Quantitative  analysis 21 

Determination  of  moisture 21 

Factors  affecting  results  of  moisture  determination ._  22 

Effect  of  volatility  of  nitroglycerin 22 

Illustrative  experiment 22 


M185893 


2  CONTENTS. 

Quantitative  analysis — Continued. 

Determination  of  moisture — Continued. 

Factors  affecting  results  of  moisture  determination — Continued.  Page. 

Effect  of  volatility  of  nitrotoluenes 24 

Volatility  over  sulphuric  acid  in  ordinary  desiccators —  25 
Effect  of  surface  area  of  sample  on  volatility  of  nitro- 
toluenes   25 

Volatility  over  sulphuric  acid  in  vacuum  desiccators 26 

Determination    of    moisture    in    explosives    containing 

"  liquid  nitrotoluenes  " 27 

Effect  of  volatility  of  mononitrobenzene 29 

Effect  of  materials  containing  water  of  crystallization 30 

Results  of  tests  with  magnesium  sulphate  and  potassium 

alum 30 

Discussion  of  results  of  experiments 31 

Extraction  with  ether —  33 

Method  of  extraction 33 

Drying  of  insoluble  residue 33 

Modified  tube  for  Wiley  extraction  apparatus 34 

Evaporation  in  the  bell-jar  evaporator. 35 

Analysis  of  ether  extract ; 36 

Effect  of  volatility  of  nitro  compounds  and  nitroglycerin  on 

the  results  of  the  analysis ; 37 

Loss  of  nitroglycerin  during  evaporation  of  the  ether 

solution - 37 

Effect  of  rate  of  air  current  on  evaporation  of  nitro- 
glycerin   39 

Loss  of  nitrotoluenes  during  evaporation  of  the  ether 

solution 39 

Conclusions  regarding  loss  by  evaporation  of  the  ether 

extract 41 

Effect  of  various  substances  on  the  determination  of  nitro- 
glycerin by  means  of  the  nitrometer 41 

Tests  of  ether-soluble  substances 42 

Discussion  of  results  of  tests 44 

Tests  to  ascertain  solubility  of  ether-soluble  substances 

in  nitroglycerin 45 

Determination  of  sulphur  in  the  ether  extract 46 

Determination  of  vaseline,  paraffin,  oils,  and  resins  in  the 

ether  extract 46 

Determination  of  nitrosubstitution  compounds  in  the  pres- 
ence  of  nitroglycerin 47 

Description   of  apparatus 47 

Operation  of  the  apparatus 49 

Determination  of  nitropolyglycerin  in  mixture  with  nitro- 
glycerin   51 

Method   for   determining  the  nitrogen  content  of  the 

mixture 51 

Boiling-point  method  for  determining  molecular  weight 

of  the  mixture 52 

The  two  methods  compared 53 

Method  for  determining  solubility  of  the  mixture 53 


CONTENTS.  3 

Quantitative  analysis^-Continued.  Page. 

Extraction  with  water 54 

Method  of  extracting  water-soluble  ingredients 54 

Drying  of  insoluble 'residue 55 

Examination  of  water  extract ' 56 

Determination  of  nonvolatile  solids 56 

Ignition  of  residue 57 

Treatment  of  residue  containing  zinc 57 

Determination  of  ammonium  salts  as  NH» 58 

Determination  of  zinc 58 

Determination  of  potassium 59 

Perchlorate  method 59 

Determination  of  nitrates  by  nitrometer  method 60 

Determination  of  nitrates  by  nitron  method 60 

Preparation   of  reagent 61 

Method   of  procedure 61 

Interference  of  other  salts 61 

Solubility  of  nitron  nitrate 61 

Recovery  of  nitron__ 62 

Determination  of  chlorates 62 

Determination  of  chlorate  by  reduction  with  sulphur 

dioxide 62 

Determination  of  chlorate  by  reduction  with  formalde- 
hyde   63 

Determination  of  perchlorates 64 

Fusion   method 64 

Nitron  method  for  determination  of  perchlorates 65 

Determination  of  nitrates,  chlorides,  chlorates,  and  perchlo- 
rates in  a  mixture 65 

Determination  of  soluble  organic  materials  in  the  water  ex- 
tract  - 66 

Determination  of  sugars 66 

Determination  of  gum  arabic 67 

Extraction  with  dilute  hydrochloric  acid 67 

Extraction  with  cold  dilute  acid 68 

Hydrolysis  with  boiling  dilute  hydrochloric  acid 68 

Solubility  of  wood  pulp  in  boiling  hydrochloric  acid  of  vary- 
ing  dilution 69 

Examination  of  acid  solution 70 

Determination  of  aluminum  and  iron 70 

Determination  of  calcium 70 

Determination  of  magnesium 70 

Determination  of  zinc 71 

Determination  of  manganese  dioxide 71 

Determination  of  calcium  silicide 71 

Extraction  with  carbon  bisulphide 72 

Determination  of  sulphur 72 

Extraction  with  acetone 72 

Determination  of  nitrocellulose  and  nitrostarch 72 

Method  of  treatment  with  acetone . 73 

Recovery  of  nitrocellulose  or  nitrostarch  from  acetone  solu- 
tion —                                 78 


4  CONTENTS. 

Quantitative  analysis — Continued.  Page. 

Examination  of  the  insoluble  residue 74 

Microscopic   examination 74 

Preparation  of  slides 74 

Determination  of  ash . 75 

The  ultimate  composition  of  carbonaceous  ingredients 76 

Ultimate  composition  of  wood  pulp 76 

Ultimate  composition  of  corn  meal 77 

Ultimate  composition  of  wheat  flour 78 

Concluding    remarks 79 

Appendix — Tolerances  for  permissible  explosives 80 

Publications  on  mine  accidents  and  tests  of  explosives 82 

Index 85 


ILLUSTRATIONS. 


Page. 
PLATE     I.  A,  B,  Wood  pulp;   (7,  Sawdust;  D,  E,  Infusorial  earth;  F, 

Crude  fiber  from  wheat  middlings, 74 

II.  A,  Cellulose;   B,  Nitrocellulose ;   C,  Wheat  flour;  D,   Wheat 

flour  and  wood  pulp ;  E,  Wheat  flour ;  F,  Corn  meal 76 

III.  A,  Peanut-shell  meal;  B,  Rice  hulls;   C,  Corncob  meal;  D, 

Vegetable-ivory  meal __ 78 

FIGURE  1.  Result  of  exposing  dry  "  60  per  cent "  dynamite  for  77  days  in 

desiccator  at  33°  to  359  C.  without  desiccating  agent 23 

2.  Results  of  exposing  "  60  per  cent "  dynamite  for  459  days  in 

desiccator  at  33°  to  35°  C.  without  desiccating  agent 24 

3.  Result  of  exposure  of  "  liquid  nitrotoluenes  "  in  vacuum  desic- 

cators    28 

4.  Modified  glass  tube  for  use  with  Wiley  extraction  apparatus—  35 

5.  Apparatus  for  evaporating  ether  extract 36 

6.  Apparatus  for  separation  of  nitrosubstitution  compounds  from 

nitroglycerin 48 

7.  Curve  of  llimit  variation  in  composition  of  permissible  ex- 

plosives   80 


THE  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 


By  C.  G.  STORM. 


INTRODUCTION. 

Permissible  explosives  are  those  that  have  passed  the  tests  pre- 
scribed by  the  Bureau  of  Mines  for  explosives  intended  for  use  in 
coal  mines,  and  are  therefore  recommended  by  the  bureau  as  suitable 
for  this  class  of  work  when  used  under  the  prescribed  conditions. 
The  tests  for  permissible  explosives  and  the  conditions  prescribed 
for  their  use  are  described  in  Miners'  Circular  6  of  the  Bureau  of 
Mines.0  Up  to  June  1,  1915,  168  explosives  had  been  classed  as  per- 
missible explosives;  133  of  them  were  then  on  the  bureau's  "per- 
missible list "  and  35  had  been  withdrawn  by  the  manufacturers. 

In  addition  to  the  required  physical  tests,  each  explosive  is  sub- 
jected to  a  complete  chemical  examination  in  order  that  its  exact 
composition  may  be  known  and  also  that  the  composition  of  future 
samples  of  the  same  explosive  collected  in  the  field  may  be  compared 
with  that  of  the  sample  which  originally  passed  the  bureau's  tests, 
for  by  such  comparison  it  may  be  possible  to  ascertain  whether  or 
not  the  explosive  as  supplied  to  the  miner  is  still  "  permissible." 

This  bulletin  is  published  primarily  for  the  purpose  of  informing 
manufacturers  of  such  explosives  as  to  the  methods  used  by  the 
Bureau  of  Mines  in  the  analysis  of  samples  received  for  tests  to 
determine  their  permissibility.  Such  information  may  be  of  value 
in  cases  of  possible  controversy  over  the  results  obtained  in  the 
analysis  of  a  field  sample  as  compared  with  those  obtained  in  ana- 
lyzing the  sample  originally  tested  by  the  bureau.  Also,  a  descrip- 
tion of  the  methods  used  by  the  Bureau  of  Mines  in  the  analysis  of 
explosives  should  be  of  assistance  to  the  many  chemists  engaged  in 
similar  analytical  work. 

ACKNOWLEDGMENTS. 

The  writer  desires  to  acknowledge  the  valuable  assistance  of  A.  L. 
Hyde,  W.  C.  Cope,  J.  H.  Hunter,  J.  E.  Crawshaw,  and  C.  A.  Taylor, 
of  the  explosives  chemical  laboratory  of  the  Bureau  of  Mines,  in 
obtaining  the  analytical  results  included  in  this  bulletin. 

«  Hall,  Clarence,  Permissible  explosives  tested  prior  to  Jan.  1,  1912,  and  precautions 
to  be  observed  in  their  use  :  Miners'  Circular  6,  Bureau  of  Mines,  1912,  20  pp. 

o 


6:  *'  -ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

S  -NATURE  OF  PERMISSIBLE  EXPLOSIVES. 


In  explosives  intended  for  use  in  open  work,  such  as  quarrying,  the 
factor  of  prime  importance  is  efficiency  in  bringing  down  the  mate- 
rial to  be  blasted.  Such  explosives  are  therefore  so  constituted 
as  to  produce  the  desired  effects  without  regard  to  the  temperature 
of  explosion,  the  amount  of  flame  produced,  or  the  nature  of  the 
gaseous  products.  The  properties  essential  to  explosives  used  in  tun- 
neling are  efficiency  and  the  absence  of  poisonous  gases  in  the  prod- 
ucts of  explosion.  Coal-mining  explosives  should  possess  not  only 
all  of  these  qualities  but  should  evolve  on  explosion  flames  of  rela- 
tively low  temperature. 

By  proper  changes  in  its  composition  or  in  the  properties  of  its 
components,  an  explosive  of  any  type  may  be  altered  so  that  on  ex- 
plosion it  will  not  ignite  an  explosive  mixture  of  coal  gas  or  coal  dust 
or  both  with  air. 

The  general  methods  in  use  at  the  present  time  for  bringing  about 
a  reduction  in  the  flame  temperature  of  explosive  mixtures  have 
been  discussed  in  another  publication  of  the  Bureau  of  Mines,0  and 
are  summarized  as  follows : 

(a)  The  addition  of  an  excess  of  carbon,  for  tlie  purpose  of  reducing  the 
amount  of  carbon  dioxide  formed. 
(&)  The  addition  of  free  water. 

(c)  The  addition  of  solids  holding  water  of  crystallization. 

(d)  The  addition  of  inert  materials. 

(e)  The  addition  of  volatile  salts. 

The  effects  of  such  additions  have  been  considered  from  the  view- 
point of  thermochemistry  in  the  publication  referred  to.  This  bul- 
letin discusses  the  variations  in  the  methods  of  chemical  analysis 
made  necessary  by  such  alterations  in  the  composition  of  the  ordi- 
nary types  of  blasting  explosives. 

CLASSIFICATION  OF  PERMISSIBLE  EXPLOSIVES. 

Permissible  explosives  have  been  classified,  according  to  their  char- 
acteristic components,  into  four  general  classes  6  as  follows : 
Class  1 — Ammonium-nitrate  explosives. 
Class  2 — Hydrated  explosives. 

Class  3 — Organic  nitrate  (other  than  nitroglycerin)  explosives. 
Class  4 — Nitroglycerin  explosives. 

8  Hall,  Clarence,  Snelling,  W.  O.,  and  Howell,  S.  P.,  Investigations  of  explosives  used 
in  coal  mines,  with  a  chapter  on  the  natural  gas  used  at  Pittsburgh,  by  G.  A.  Burrell,  and 
an  introduction  by  C.  E.  Munroe :  Bull.  15,  Bureau  of  Mines,  1912,  pp.  51-58. 

*Hall,  Clarence,  Permissible  explosives  tested  prior  to  Jan.  1,  1912,  and  precautions 
to  be  taken  In  their  use  :  Miners'  Circular  6,  Bureau  of  Mines,  1912,  pp.  12-14  ;  Permissible 
explosives  tested  prior  to  Jan.  1,  1914 :  Tech.  Paper  71,  Bureau  of  Mines,  1914,  pp.  8-10. 


GENERAL  CHARACTERISTICS.  7 

Of  the  168  explosives  which  passed  the  bureau's  tests  for  permis- 
sibility up  to  June  1,  1915,  75  were  explosives  of  class  1,  9  were  of 
class  2,  9  were  of  class  3,  and  75  were  of  class  4.  Of  the  35  of  these 
which  have  been  withdrawn  from  the  list  14  were  of  class  1,  3  of 
class  2,  6  of  class  3,  and  12  of  class  4. 

Although,  up  to  June  1, 1915,  no  explosives  containing  chlorates  or 
perchlorates  as  their  characteristic  ingredients  have  been  placed 
upon  the  bureau's  permissible  list,  a  number  of  such  explosives  have 
been  tested  by  the  bureau.  The  chlorate  or  perchlorate  explosives 
form  an  additional  class  to  the  four  classes  enumerated  above,  but 
because  they  are  presented  for  testing,  methods  for  their  analysis  are 
discussed  herein. 

GENEKAL    CHAEACTERISTICS    OF    PERMISSIBLE 
EXPLOSIVES. 

AMMONIUM  NITRATE  EXPLOSIVES. 

Ammonium  nitrate,  although  not  commonly  regarded  as  an  explo- 
sive substance,  has  been  shown  to  be  capable  of  explosive  decomposi- 
tion. Berthelot  °  gives  seven  different  decomposition  reactions  of  am- 
monium nitrate,  three  of  which  are  explosive  in  their  nature.  The 
maximum  effect  is  produced  by  the  reaction — 

2NH4NO3=4H2O+O2+2N2, 

which  results  under  the  influence  of  sudden  high  temperature  and 
pressure,  as  by  the  action  of  a  strong  detonator.  The  effect  of  weaker 
detonators  is  to  produce  other  forms  of  decomposition,  yielding 
oxides  of  nitrogen. 

Lobry  de  Bruyn&  succeeded  in  detonating  a  charge  of  180  grams 
of  pure  ammonium  nitrate  compressed  in  an  8-cm.  shell,  using"  a 
priming  charge  of  20  to  30  grams  of  Bellite  (a  mixture  of  ammonium 
nitrate  and  dinitrobenzene),  and  a  detonator  containing  1  gram  of 
mercury  fulminate.  The  shell  was  disrupted  into  many  fragments. 
Without  the  priming  charge  of  Bellite,  a  detonator  containing  3 
grams  of  mercury  fulminate  produced  only  incomplete  explosion  of 
the  ammonium  nitrate. 

Lheurec  obtained  complete  detonation  of  cartridges  of  pure  am- 
monium nitrate  loaded  in  drill  holes  in  rock,  using  a  detonating  fuse 
(cordeau  detonant)  of  trinitrotoluene  as  the  initial  detonator,  the 
fuse  passing  completely  through  the  cartridge. 

a  Berthelot,  M.f  Sur  la  force  des  matieres  explosives,  t.  2,  1883,  p.  183. 

6  Lobry  de  Bruyn,  C.  A.,  Sur  I'explosivite"  de  1'azotate  d'ammonium  :  Rec.  trav.  chim. 
Pays-Bag,  t.  10,  1891,  pp.  127-131 ;  Escales,  R.,  Die  Explosivstoffe,  Bd.  4,  1909,  p.  40. 

0  Lheure,  — ,  Note  sur  I'amllioration  de  la  se*curit<§  dans  les  mines  grisouteuses  par 
eraploi  d'un  nouveau  dispositif  d'amorcage  des  explosifs :  Ann.  des  mines,  s6r.  10,  t.  12, 
1907,  p.  169 ;  Escales,  R.,  Die  Explosivstoffe,  Bd.  4,  1909,  p.  130. 


8  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

The  temperature  of  explosion,  as  calculated  from  the  above  reac- 
tion, is  only  1,121°  C.,a  much  lower  than  the  calculated  temperatures 
resulting  from  the  usual  types  of  permissible  coal-mining  explosives, 
which  generally  vary  between  1,500°  and  2,000°  C.  Its  insensitive- 
ness  and  relatively  low  explosion  pressure,  however,  prevent  pure 
ammonium  nitrate  per  se  from  having  any  practical  application  as  a 
blasting  explosive. 

By  the  admixture  of  suitable  combustible  materials,  this  insensi- 
tiveness  is  overcome  and  explosives  of  greater  strength  are  obtained. 
As  has  been  noted,  a  large  proportion  of  the  explosives  which  have 
been  placed  on  the  bureau's  permissible  list  are  of  this  type,  the  list 
on  June  1,  1915,  including  61  ammonium-nitrate  explosives  out  of  a 
total  of  133  explosives;  14  other  ammonium-nitrate  explosives  for- 
merly on  the  permissible  list  have  been  withdrawn. 

The  materials  used  as  sensitizers  for  ammonium  nitrate  may  be 
(1)  explosive  or  (2)  nonexplosive.  The  first  group  of  sensitizers 
comprises  nitroglycerin,  nitrocellulose,  nitrosubstitution  compounds, 
or  mixtures  of  two  or  more  of  these  substances.  The  second  group 
includes  various  nonexplosive  combustible  materials,  such  as  resins, 
sulphur,  carbonized  curcuma  powder,  cereal  flour,  sugar,  hydrocarbon 
oils  or  other  oils,  paraffin,  and  coal. 

HYDBATED    EXPLOSIVES. 

Under  the  designation  "hydrated  explosives"  are  included  those 
that  depend  for  reduction  of  their  flame  temperature  largely  upon 
the  cooling  effect  of  water  in  the  form  of  water  of  crystallization  of 
certain  salts  included  in  their  composition. 

The  list  of  "permissible  explosives"  included,  on  June  1,  1915, 
6  explosives  under  this  classification  and  3  others  previously  in  this 
class  had  been  withdrawn. 

The  hydrated  salts  used  in  these  explosives  are  Epsom  salt 
(MgSO4.7H2O),  or  potassium  alum  [K2A12(SO4)4.24H2O],  contain- 
ing respectively  51.22  per  cent  and  45.57  per  cent  water  of  crystalliza- 
tion. 

Certain  explosives  included  in  other  classes  of  "permissible  ex- 
plosives "  also  contain  these  hydrated  salts,  as  well  as  aluminum  sul- 
phate [A12(SO4)3.18H2O],  with  48.81  per  cent  of  water  or  gypsum 
(GaSO4.2H2O),  with  20.92  per  cent  of  water,  but  not  in  sufficient 
quantities  to  justify  their  classification  as  hydrated  explosives. 

~"a  Hall,  Clarence,  Snelling,  W.  O.,  and  Howell,  S.  P.,  Investigations  of  explosives  used 
in  coal  mines,  with  a  chapter  on  the  natural  gas  used  at  Pittsburgh,  by  G.  A.  Burrell, 
and  an  introduction  by  C.  E.  Munroe  :  Bull.  15,  Bureau  of  Mines,  1912,  p.  32.  Other 
calculated  values  for  the  temperature  of  explosion  of  ammonium  nitrate  are  1,134°  C. 
(Heise)  and  1,130°  C.  (French  Explosives  Commission),  given  by  Escales,  It.,  Die  Explo- 
sivstoffe,  Bd.  4,  1909,  p.  47. 


GENEKAL  CHARACTERISTICS.  9 

The  hydrated  explosives  all  contain  nitroglycerin  as  the  principal 
explosive  ingredient,  and  most  of  them  also  contain  ammonium 
nitrate  and  various  other  components  common  to  explosives  of  other 
classes. 

ORGANIC  NITRATE    (OTHER  THAN  NITROGLYCERIN)    EXPLOSIVES. 

The  "permissible  list"  on  June  1,  1915,  included  only  3  ex- 
plosives of  this  class ;  6  others  had  previously  been  withdrawn  from 
the  list. 

This  class  includes  explosives  containing  nitrostarch a  or  other  or- 
ganic nitrate  as  their  characteristic  ingredient. 

Nitrostarch,  without  the  admixture  of  other  ingredients  which  re- 
duce its  brisance  and  high  explosion  temperature,  and  modify  other 
of  its  properties,  is  unsuited  for  use  as  a  coal-mining  explosive.  The 
temperature  of  explosion  of  nitrostarch  containing  12.75  per  cent 
nitrogen  is,  as  calculated  by  the  writer,  approximately  2,340°  C., 
which  is  considerably  higher  than  the  explosion  temperatures  of 
permissible  explosives.6  Furthermore,  the  products  of  explosion  of 
nitrostarch  include  larger  amounts  of  carbon  monoxide  than  are 
desirable  in  mining  explosives.  By  suitable  additions  of  oxidizing 
agents  and  heat-absorbing  materials,  it  is  possible,  however,  to  pre- 
pare nitrostarch  explosives  answering  all  requirements  of  permissible 
explosives. 

NITROGLYCERIN    EXPLOSIVES. 

The  classification  "nitroglycerin  explosives"  includes  those  ex- 
plosives whose  characteristic  ingredient  is  nitroglycerin  which  are 
not  included  in  the  class  of  "  hydrated  explosives." 

Of  the  133  explosives  on  the  "  permissible  list,"  June  1,  1915,  63 
were  included  in  this  class,  and  12  others  previously  in  this  class  had 
been  withdrawn  from  the  list  before  that  date. 

The  ingredients  used  in  explosives  of  this  class  include  practi- 
cally all  those  entering  into  the  composition  of  explosives  of  the 
various  other  classes. 

Permissible  explosives  of  the  nitroglycerin  class  may  be  regarded 
as  modified  dynamites,  in  which  any  of  the  general  methods  men- 
tioned on  page  6,  or  combinations  of  these  methods,  may  be  em- 
ployed for  reducing  the  amount  and  temperature  of  the  flame  pro- 
duced by  explosion. 

0  The  term  "  nitrostarch  "  is  used  in  this  bulletin  because  of  its  acceptance  in  general 
usage.  The  correct  chemical  designation  is  starch  nitrate. 

"See  Hall,  Clarence,  Snelling,  W.  O.,  and  Howell,  S.  P.,  Investigations  of  explosives 
used  in  coal  mines,  with  a  chapter  on  the  natural  gas  used  at  Pittsburgh,  by  G.  A.  Burrell, 
and  an  introduction  by  C.  E.  Munroe :  Bull.  15,  Bureau  of  Mines,  1912,  p.  28. 


10  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

PHYSICAL  EXAMINATION  OF  PEEMISSIBLE 
EXPLOSIVES. 

Among  the  requirements  which  must  be  met  by  an  explosive  in 
order  that  it  may  be  classed  as  a  "  permissible  explosive  "  are  found 
the  following :  ° 

"An  explosive  will  be  considered  unsatisfactory  if  it  is  not  chemi- 
cally stable,  if  it  shows  leakage  of  nitroglycerin,  or  if  it  is  in  such 
condition  that  exudation  of  nitroglycerin  would  occur  in  handling 
or  transportation." 

It  is  therefore  important  that  tests  be  made  on  each  sample  of 
explosive  to  determine  its  stability  and  liability  to  exude  nitro- 
glycerin. In  addition  to  these  tests  the  determination  of  gravimetric 
density  is  included  as  part  of  the  physical  examination. 

DETERMINATION   OF   GRAVIMETRIC   DENSITY. 

0 
The  determination  of  gravimetric  density  or  apparent  specific 

gravity  of  the  cartridge  of  explosive  has  been  already  described  in 
a  former  publication.6  The  volume  of  the  entire  cartridge  is  found 
by  determining  the  amount  of  uniform  sand,  of  previously  deter- 
mined gravimetric  density,  displaced  by  the  cartridge.  The  weight 
of  the  cartridge  in  grams  divided  by  its  volume  in  cubic  centimeters 
gives  the  apparent  specific  gravity  or  gravimetric  density  of  the 
cartridge. 

TESTS   FOR   LIABILITY   OF   EXUDATION. 

The  three  general  methods  for  determining  the  liability  of  exuda- 
tion of  liquid  ingredients  from  cartridges  of  an  explosive  have  been 
described  for  the  ordinary  types  of  dynamites.0  These  methods  are 
employed  in  the  same  manner  for  "permissible  explosives."  The 
method  generally  employed  in  the  bureau's  laboratory  is  the  cen- 
trifugal method,  in  which  8-gram  samples  of  the  explosive,  each 
contained  in  an  ordinary  porcelain  Gooch  crucible  without  a  mat, 
are  centrifuged  for  5  minutes  at  a  speed  of  600  revolutions  per 
minute,  the  circle  of  rotation  made  by  the  bottom  of  the  crucibles 
being  28  centimeters  in  diameter.  Any  exuding  nitroglycerin  is 
absorbed  in  a  small  quantity  of  cotton  placed  in  an  ordinary  porce- 
lain crucible  suspended  beneath  the  Gooch  crucible. 

The  temperature  at  which  the  test  is  made  should  be  approximately 
20°  C.  Under  these  conditions  a  loss  of  more  than  5  per  cent  of  the 
original  weight  of  the  sample  is  considered  by  the  bureau  to  indi- 

•  Fees  for  testing  explosives,  Bureau  of  Mines,  Schedule  1,  Sept.  17,  1913,  8  pp. 
6  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite,  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  7-8. 

«  Snelling,  W.  O.,  and  Storm,  C.  G.,  Op.  cit.,  pp.  8-10. 


PHYSICAL  EXAMINATION.  11 

cate  liability  of  leakage  of  nitroglycerin  from  the  cartridges  in  trans- 
portation or  storage. 

It  should  be  noted,  however,  that  exudation  is  much  less  liable  to 
occur  in  explosives  of  the  "  permissible  "  type  than  in  ordinary  grades 
of  dynamite  because  of  the  smaller  content  of  nitroglycerin  in  most 
explosives  of  the  former  class. 

TESTS  FOR  STABILITY. 
ABEL  TEST. 

All  samples  of  explosives  submitted  to  the  bureau  are  tested  by 
the  Abel  heat  test,  a  full  description  of  which  has  been  published  by 
the  bureau.0  Briefly,  the  test  depends  upon  the  time  required  for 
the  production  of  a  brownish  line  of  discoloration  of  standard  in- 
tensity on  a  strip  of  potassium  iodide-starch  paper  suspended  above 
the  explosive  in  a  glass  test  tube  by  the  oxides  of  nitrogen  liberated 
from  the  explosive  when  the  sample  is  heated  in  a  water  bath  at 
a  constant  temperature.  The  test  is  made  in  duplicate,  on  samples 
weighing  2  grams  each,  at  a  temperature  of  71°  C.  ±0.5°  C.  An 
explosive  is  considered  to  be  of  unsatisfactory  stability  when  the  tune 
of  the  test  is  less  than  10  minutes. 

"  INTERNATIONAL  "  75°   TEST.      !fr\ 

The  "preliminary  test"  recommended  by  the  international  com- 
mission which  reported  to  the  Eighth  International  Congress  of 
Applied  Chemistry,  1912,  on  "  Methods  for  Testing  the  Stability  of 
Explosives,"6  is  made  use  of  to  supplement  the  Abel  test.  This 
test  is  made  as  follows : 

METHOD  OF  MAKING  THE  TEST. 

Two  samples  of  explosive  of  10  grams  each,  without  previous 
drying,  are  placed  in  glass  tubes  35  mm.  in  diameter  and  50  mm.  in 
height;  the  tubes  are  loosely  covered  with  watch  glasses  and  heated 
for  48  hours  in  a  constant-temperature  oven  at  75°  C. 

At  the  end  of  this  period  of  heating  the  samples  are  examined  for 
signs  of  decomposition,  as  indicated  by  change  of  appearance  or  by 
odor  or  the  presence  of  nitrous  fumes  in  the  tube.  The  explosive  is 
considered  to  be  of  unsatisfactory  stability  if  positive  indication  of 
decomposition  is  noted. 

In  order  to  gain  additional  information  as  to  the  behavior  of  ex- 
plosives under  the  conditions  of  this  test,  in  tests  by  the  bureau  the 

•  Snelltng,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite,  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  10-12. 

b  Commision  Internationale  pour  L'Etude  de  L'Unifi cation  des  Methodes  D'Epreuves  sur 
la  Stabilite  des  Explosifs  ;  Rapport,  final  approve"  le  25  Juillet  1912,  pour  6tre  pre*sente" 
au  VIII"1*  Congres  International :  Original  Communications,  Eighth  Int.  Cong.  App.  Chem., 
vol.  25,  September,  1912,  p.  261. 


12  ANALYSIS  OP   PERMISSIBLE   EXPLOSIVES. 

tubes  containing  the  samples  have  been  accurately  weighed  before 
and  after  heating  at  75°  C.  and  the  loss  of  weight  noted  in  terms 
of  percentage  of  the  weight  of  original  sample.  Any  marked  decom- 
position of  the  explosive  or  of  any  of  its  components  would  be  indi- 
cated by  a  considerable  loss  of  weight  in  excess  of  the  moisture  con- 
tent of  the  explosive,  due  consideration  being  made  for  the  fact  that 
some  loss  from  volatilization  of  nitrpglyjcerin,  or  possibly  of  other 
constituents,  will  result  during  such  heating. 

COMPARISON  OF  RESULTS  OF  "  ABEL  "  AND  "  INTERNATIONAL  "  TESTS. 

As  a  general  rule,  the  loss  of  weight  noted  in  testing  stable  explo- 
sives by  this  method  is  but  a  small  amount  in  excess  of  the  moisture 
content,  the  difference  being  usually  less  than  0.5  per  cent  and  rarely 
exceeding  1  per  cent.  One  explosive  of  doubtful  stability,  which  con- 
tained among  other  ingredients  nitroglycerin,  potassium  chlorate,  and 
ammonium  nitrate  (a  very  unusual  and  dangerous  mixture),  gave  an 
Abel  test  of  only  7  to  9  minutes,  and  on  being  subjected  to  the  "  in- 
ternational "  75°  test  it  evolved  odors  of  chlorine  and  oxides  of  nitro- 
gen and  lost  nearly  5  per  cent  in  weight  in  excess  of  the  moisture 
content. 

A  large  number  of  tests  made  by  the  "  international  "  method  in  the 
bureau's  laboratory  have  substantiated  the  results  of  the  Abel  test. 

SAMPLING  AND  PREPARATION  FOR  ANALYSIS. 

The  test  requirements  provide  that  samples  of  100  pounds  of  each 
explosive  to  be  tested  for  permissibility  must  be  submitted  to  the 
bureau  by  the  manufacturer.  From  this  large  sample,  4  to  6  car- 
tridges are  selected  at  random  for  chemical  examination.  A  sample 
for  analysis  is  prepared  by  removing  the  paper  wrapper,  care  being 
taken  that  particles  of  paraffin  from  the  outside  of  the  wrapper  do 
not  become  mixed  with  the  explosive,  cutting  off  with  a  horn  spatula 
3  to  5  cm.  of  each  end  of  the  cartridge  and  mixing  thoroughly 
the  centraf  parts  of  each  cartridge  in  a  porcelain  dish  with  a  large 
horn  spoon.  The  explosive  is  reduced  to  a  mass  of  such  uniformity 
as  the  fineness  of  the  ingredients  will  permit,  all  hard  masses  of  par- 
ticles being  broken  up  by  means  of  the  spoon.  After  very  thorough 
mixing  of  the  sample,  a  wide-mouthed  sample  bottle  of  about  250  c.  c. 
capacity  is  filled  by  taking  portions  with  the  spoon  from  different 
parts  of  the  entire  mass  in  the  dish.  The  sample  in  the  bottle  should 
be  remixed  immediately  before  analysis  in  order  to  compensate  for 
any  segregation  of  liquid  ingredients.  Experiments  have  demon- 
strated that  appreciable  segregation  may  occur  in  even  a  few  days.® 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite,  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  14-15. 


QUALITATIVE   ANALYSIS. 


13 


QUALITATIVE  ANALYSIS. 

In  order  to  decide  upon  the  method  of  quantitative  analysis  to  be 
followed,  it  is  essential  that  first  a  complete  qualitative  analysis  of 
the  explosive  should  be  made.  After  such  examination  has  shown 
the  identity  of  the  components  of  the  explosive  mixture,  the  proper 
methods  for  quantitative  separation  or  determination  of  these  com- 
ponents can  then  be  chosen. 

The  general  methods  for  the  qualitative  analysis  of  permissible 
explosives  are  the  same  as  those  described  in  Bulletin  51 a  for  ordi- 
nary types  of  dynamite.  It  should  be  noted,  however,  that  many 
substances  are  employed  as  constituents  of  the  low-flame  explosives 
which  are  not  found  in  ordinary  blasting  explosives. 

COMPONENTS    OF   LOW-FLAME   EXPLOSIVES. 

Below  is  given  a  list  of  some  of  the  substances  which  have  been 
found  in  low-flame  explosives.  Most  of  them  have  been  identified  as 
constituents  of  explosives  manufactured  in  this  country;  a  few  are 
ingredients  of  foreign  explosives. 

These  substances  are  classified  according  to  their  solubility  in  the 
general  scheme  usually  followed  in  analysis. 

Some  components  of  loio-flame  explosives. 
Soluble  in  ether. 


Asphaltum. 
Nitrobenzenes. 
Nitroglycerin. 
Nitronaphthalenes. 
Nitropolyglycerin. 
Nitrotoluenes. 
Oils    (mineral   or   vege- 
table). 
Paraffin. 
Resins. 
Sulphur. 
Vaseline. 

Soluble  in  acid, 

Aluminum. 
Calcium  carbonate. 
Calcium  silicide.  ' 
Ferric  oxide.0 
Magnesium  carbonate. 
Manganese  dioxide.0 
Zinc. 
Zinc  oxide.6 


Soluble  in  water, 

Alum  (crystals). 

Aluminum  sulphate 
(crystals). 

Ammonium  chloride. 

Ammonium  nitrate. 

Ammonium  oxalate. 

Ammonium  perchlorate. 

Ammonium  sulphate. 

Barium  nitrate. 

Calcium  sulphate  (crys- 
tals). 

Gums. 

Magnesium  sulphate 
(crystals). 

Potassium  bichromate. 

Potassium  chlorate. 

Potassium  nitrate. 

Potassium  perchlorate. 

Potassium  sulphate. 

Sodium  bicarbonate. 

Sodium  carbonate. 

Sodium  chloride. 

Sodium  nitrate. 


Sodium  sulphate. 

Sugar. 

Zinc  oxide.6 

Insoluble. 

Charcoal. 

Clay. 

Coal. 

Corn  meal. 

Corncob  meal. 

Graphite. 

Kieselguhr. 

Nitrated  wood. 

Nitrocellulose. 

Nitrostarch. 

Peanut-shell  meal. 

Powdered  slate. 

Rice  hulls. 

Sand. 

Sawdust. 

Turmeric. 

Vegetable  ivory  meal. 

Wheat  flour. 

Wood  pulp. 


0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite,  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  16-19. 

*  Generally  found  partly  or  wholly  in  the  water  extract  owing  to  its  solubility  in  am- 
monium-nitrate solutions. 

c  Partly  soluble  in  the  dilute  acid  used. 

10293°— Bull.  96—16 2 


14  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

METHOD    OF    CONDUCTING   QUALITATIVE    ANALYSIS.- 

In  conducting  the  qualitative  examination  of  a  permissible  ex- 
plosive it  is  usually  advisable  to  separate  its  components  into  groups, 
as  indicated  above,  by  successive  extractions  with  ether,  water,  and 
dilute  hydrochloric  acid  (1 :10),  so  that  the  identification  of  the  vari- 
ous ingredients  present  is  much  simplified. 

These  extractions  are  conveniently  made  by  shaking  a  rather  large 
sample  (about  25  grams)  of  the  explosive  with  ether  in  a  large  stop- 
pered test  tube,  filtering  the  solution  through  a  paper  filter  and  treat- 
ing the  residue  once  or  twice  again  with  fresh  ether  in  the  same  man- 
ner. The  ether  solution  is  evaporated,  and  the  insoluble  residue,  after 
drying  to  remove  adhering  ether,  is  treated  in  a  similar  manner  with 
water,  and  finally  with  dilute  hydrochloric  acid. 

SPECIAL  QUALITATIVE  TESTS. 

Tests  for  some  of  the  more  unusual  substances,  not  generally  found 
in  the  ordinary  types  of  blasting  explosives,  are  made  as  follows: 

TEST  FOR  NITROPOLYGLYCERIN. 

In  making  a  test  for  nitropolyglycerin  the  ether  extract,  after 
evaporation  of  the  ether,  is  filtered  through  a  paper  filter  in  order  to 
separate  any  insoluble  oily  or  resinous  materials.  Some  of  the  clear 
filtrate  is  tested  for  nitrosubstitution  compounds  by  means  of  the 
color  test  described  in  Bulletin  51.°  In  the  absence  of  nitrosubstitu- 
tion compounds  the  filtrate  is  tested  for  nitropolyglycerin  by  deter- 
mining its  solubility  in  a  mixture  of  60  parts  glacial  acetic  acid  and 
40  parts  water,  as  described  on  page  53.  This  test  readily  detects 
nitropolyglycerin  in  admixture  with  nitroglycerin. 

TEST  FOR  MONONITRONAPHTHALENE. 

Mononitronaphthalene  is  readily  detected  in  the  residue  obtained 
by  evaporation  of  the  ether  extract  by  adding  a  drop  of  this  material 
to  a  mixture  of  about  equal  parts  of  strong  sulphuric  acid  and  water. 
Mononitronaphthalene,  if  present,  causes  a  brilliant  red  color. 

TEST  FOR   CHLORIDES,   CHLORATES,   AND  PERCHLORATES. 

Chlorides,  chlorates,  and  perchlorates  in  a  mixture  are  identified  as 
follows :  Some  of  the  solution  in  water  is  acidified  with  a  few  drops  of 
nitric  acid,  an  excess  of  silver  nitrate  added,  the  mixture  heated  to 
boiling,  shaken  well  to  coagulate  the  precipitate  of  silver  chloride, 
and  filtered.  To  the  clear  filtrate  a  few  cubic  centimeters  of  formalde- 
hyde (40  per  cent  solution)  is  added  and  the  mixture  is  then  boiled. 

«  Snelling,  W.  OM  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite,  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  17-18. 


QUALITATIVE  ANALYSIS.  15 

The  formaldehyde  reduces  any  chlorate  present  to  chloride,  which  is 
precipitated  as  silver  chloride  by  the  excess  of  silver  nitrate  present. 
The  reaction  is  practically  complete  if  the  mixture  is  allowed  to  stand 
on  the  steam  bath  for  about  an  hour,  although  a  considerably  longer 
time  is  required  for  quantitative  reduction. 

The  precipitate  is  filtered  off  and  the  filtrate  evaporated  to  dry- 
ness  to  remove  excess  of  nitric  acid,  transferred  with  a  small  volume 
of  water  to  a  crucible,  enough  dry  sodium  carbonate  added  to  fill 
the  crucible,  the  mixture  dried  carefully  over  a  burner,  and  fused. 
The  fused  mass  is  dissolved  in  dilute  nitric  acid.  If  perchlorates  are 
present,  the  solution  will  be  found  to  contain  a  precipitate  of  silver 
chloride. 

TEST    FOR    SUGAR. 

The  presence  of  any  appreciable  quantity  of  organic  substances  in 
the  solution  in  water  is  indicated  by  a  more  than  slight  charring  of 
the  residue,  obtained  by  evaporating  the  solution,  when  it  is  heated 
over  a  burner.  Sugar  is  tested  for  by  acidifying  some  of  the  water 
solution  with  a  little  dilute  hydrochloric  acid,  heating  to  boiling  in 
order  that  any  cane  sugar  present  may  be  inverted,  neutralizing  with 
potassium  hydroxide,  and  boiling  with  Fehling's  solution.  A  pre- 
cipitation of  reduced  cuprous  oxide  indicates  the  presence  of  sugar. 

TEST    FOR  GUM    ARABIC. 

Gum  arabic  is  precipitated  by  the  addition  of  a  solution  of  basic 
lead  acetate  to  the  water  extract.  (See  quantitative  determination  of 
gum  arabic,  p.  67. ) 

TEST  FOR  NITROSTARCH. 

Nitrostarch  in  the  residue  left  after  extracting  the  water-soluble 
ingredients  is  detected  by  examining  a  small  portion  of  the  residue 
under  the  microscope.  (See  p.  74.)  Nitrostarch  is  readily  distin- 
guished from  unnitrated  starch  by  moistening  the  residue  under  the 
microscope  with  a  drop  of  solution  of  iodine  in  potassium  iodide ;  the 
unnitrated  starch  granules  are  colored  dark  blue  by  the  iodine  solu- 
tion, whereas  nitrostarch  granules  are  not  affected. 

TEST   FOR    NITROCELLULOSE. 

Nitrocellulose  is  readily  distinguished  from  nitrostarch  by  means 
of  the  microscope,  but  when  present  in  small  amounts  may  be  over- 
looked. The  dried  residue  insoluble  in  water  should  be  treated  with 
acetone  and  the  acetone  extract  poured  into  hot  water  in  order  to 
volatilize  the  acetone  and  precipitate  any  dissolved  nitrocellulose. 
The  white  precipitate  may  be  dried  and  identified  as  nitrocellulose  or 
nitrostarch  by  its  rapid  burning  on  being  ignited  with  a  flame.  Of 


16  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

course,  this  last  test  will  not  distinguish  between  nitrocellulose  and 
nitrostarch. 

IDENTIFICATION  OF  WOOD  PULP  MIXED  WITH   CEREAL  PRODUCTS. 

The  following  test  devised  by  Le  Roy0  has  been  found  valuable 
for  the  identification  of  small  amounts  of  wood  pulp  mixed  with 
various  cereal  products. 

One  gram  of  phloroglucinol  is  dissolved  in  15  c.  c.  of  ethyl  alcohol 
(90  to  95  per  cent)  and  10  c.  c.  of  sirupy  phosphoric  acid  is  added. 
Then  0.5  c.  c.  of  this  reagent  is  rubbed  with  a  little  of  the  sample  in 
a  porcelain  dish.  The  wood  fibers  quickly  become  colored  a  rose 
tint,  gradually  turning  to  carmine. 

This  test  was  tried  by  the  author  on  coarse  and  fine  wheat  flour 
and  on  corn  meal  with  negative  results.  A  very  small  proportion  of 
wood  pulp  mixed  with  these  cereals  was  indicated  by  red  spots 
throughout  the  mixture.  Examination  under  the  microscope  showed 
that  each  fiber  of  the  wood  pulp  was  colored  a  bright  carmine, 
whereas  the  starch  granules  and  cereal  fibers  were  unchanged  in 
color. 

Less  than  0.5  per  cent  of  wood  pulp  in  an  explosive  containing  36 
per  cent  of  corn  meal  was  readily  detected.  Such  amounts  of  wood 
pulp  may  enter  into  the  composition  of  an  explosive  from  imperfect 
cleaning  of  the  mixing  bowl  after  a  previous  mixing. 

IDENTIFICATION    OF    WHEAT    FLOUR    AND    CORN    MEAL. 

The  following  tests 6  have  been  found  of  assistance  in  distinguish- 
ing between  finely  ground  white  corn  meal  and  coarse  wheat  flour : 

GLYCERIN    TEST. 

About  1  gram  of  the  material  is  treated  with  15  c.  c.  of  glycerin 
and  boiled  for  a  few  minutes.  Corn  is  indicated  by  the  well-known 
pop-corn  odor. 

This  test  was  tried  separately  on  both  corn  meal  and  wheat  mid- 
dlings. At  first  the  difference  in  odor  was  hardly  appreciable,  but 
after  a  few  minutes  of  boiling  the  wheat  darkened  to  a  brown  color 
and  gave  an  unpleasant  "  burnt "  odor,  whereas  the  corn  meal  con- 
tinued to  evolve  the  pleasant  odor  of  pop  corn. 
• 

ALKALI    TEST. 

A  small  quantity  of  the  material  is  treated  with  10  c.  c.  of  a  1.8 
per  cent  solution  of  potassium  hydroxide  and  allowed  to  stand  for 
about  two  minutes  in  a  test  tube ;  it  is  then  made  nearly  neutral  with 

0  Le  Roy,  G.  A.,  Recherche  de  la  sciure  (fleurage)  de  bois  dans  les  farines  :  Ann.  chim. 
anal.,  t.  4,  1899,  p.  221 ;  Allen,  A.  H.,  Commercial  organic  analysis,  vol.  1,  1905,  p.  462. 
6  Allen,  A.  H.,  Loc.  cit. 


QUALITATIVE   ANALYSIS.  17 

dilute  hydrochloric  acid.     The  formation  of  a  stiff,  gelatinous  mass 
indicates  wheat  starch,  whereas  cornstarch  is  not  altered. 

This  test  and  the  glycerin  test  are  of  use  mainly  when  the  residue 
left  after  extraction  with  water  contains  no  ingredients  other  than 
wheat  flour  or  corn  meal. 

MECHANICAL  SEPARATION  OF  SOLID  INGREDIENTS. 

It  is  frequently  difficult,  in  analyzing  a  permissible  explosive  that 
contains  a  number  of  water-soluble  ingredients,  to  ascertain  defi- 
nitely the  manner  in  which  the  various  acid  and  basic  ions,  found  in 
the  water  extract  by  qualitative  tests  and  quantitatively  determined 
by  gravimetric  or  volumetric  methods,  were  combined  in  the  original 
explosive.  The  difficulties  are  similar  to  those  encountered  in  report- 
ing the  results  of  water  analyses.  The  water  analyst  usually  solves 
the  difficulty  by  reporting  the  positive  and  negative  ions  separately 
without  attempting  to  determine  their  actual  combinations.  It  is 
necessary,  however,  that  the  report  of  the  analysis  of  a  permissible 
explosive  should  give  definite  information  as  to  the  various  salts 
present. 

As  an  instance  of  such  mixtures,  a  solution  giving  tests  for  Na, 
NH4,  Cl,  and  No3,  may  be  examined  quantitatively  and  the  amount 
of  each  of  these  ions  present  accurately  determined,  without  definite 
knowledge  being  obtained  as  to  whether  the  salts  contained  in  the 
water  solution  were  (a)NaNO3,  NH4NO3,  NaCl  and  NH4C1,  or  (&) 
NaNO3  and  NH4C1,  or  (c)  NH4NO3  and  NaCl. 

Although  chemical  analysis  of  such  a  water  extract  offers  no  means 
of  determining  its  true  composition,  the  writer  has  found  that  it  is 
often  possible  to  gain  considerable  information  by  a  mechanical  sep- 
aration of  the  original  solid  ingredients  before  dissolving  in  water. 
Such  mechanical  separation  is  facilitated  by  the  fact  that  the  ingre- 
dients of  explosives  are  frequently  not  finely  pulverized  in  the  course 
of  manufacture. 

SEPARATION    OF   INGREDIENTS    BY    SCREENING. 

The  separation  is  carried  out  as  follows: 

A  sample  of  25  to  50  grams  of  the  original  explosive  is  washed 
several  times  with  ether  in  order  to  remove  the  nitroglycerin,  oily 
materials,  or  other  ether-soluble  substances;  the  residue  is  dried  a 
short  time  until  the  adhering  ether  has  evaporated,  and  then  sifted 
through  a  set  of  sieves.  The  coarser  sieves  (10  and  20  mesh)  will 
usually  be  found  to  retain  more  or  less  material  consisting  of  coarse 
fragments  of  wood  pulp  or  other  carbonaceous  absorbent,  together 
with  coarse  crystals  of  the  water-soluble  ingredients  that  have  es- 
caped pulverization  or  have  purposely  been  incorporated  in  a  coarse 


18  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

condition.  This  coarse  material  is  spread  out  on  a  piece  of  glazed 
paper  and  crystals  of  similar  appearance  sorted  out  by  the  aid  of  a 
pair  of  forceps.  A  few  fragments  or  crystals  of  each  kind  may  be 
separately  tested  qualitatively  and  readily  identified.  Much  infor- 
mation can  often  be  gained  by  dissolving  a  single  crystal  in  a  drop 
of  water  on  a  microscope  slide,  allowing  the  water  to  evaporate,  and 
examining  the  resulting  crystals  under  the  microscope,  with  or  with- 
out the  polarizing  attachment.  Many  substances  are  easily  identified 
in  this  manner.  A  single  crystal  may  be  dissolved  in  1  or  2  c.  c.  of 
water,  the  solution  divided  into  several  small  parts,  and  separate 
tests  made  on  each  part,  a  process  which  may  serve  absolutely  to 
identify  the  crystal. 

Among  many  instances  in  which  mechanical  separation  has  been 
useful  are  the  following: 

1.  An  explosive  contained,  among  other  ingredients,  ammonium 
nitrate,  ammonium  sulphate,  crystallized  potassium  alum,  potassium 
sulphate,  and  coal.    By  sifting  and  picking  over  the  coarser  crystals, 
coal,  alum,  ammonium  nitrate,  and  ammonium  sulphate  were  sep- 
arated and  positively  identified. 

2.  From  another  explosive,  sodium  nitrate,   ammonium  nitrate, 
crystallized  magnesium  sulphate,  and  corn  meal  were  separated  and 
identified. 

3.  From  a  third  explosive,  crystalline  trinitrotoluene,  alum,  and 
ammonium  nitrate  were  isolated. 

In  each-  of  these  instances  the  identification  of  these  constituents 
enabled  the  actual  composition  of  the  mixtures  to  be  calculated  from 
the  results  of  the  quantitative  analysis  without  "  guesswork  "  as  to  the 
manner  in  which  the  various  bases  and  radicles  were  combined. 

SPECIFIC-GRAVITY  SEPARATION  OF  INGREDIENTS. 

Another  method,  which  is  much  used  in  the  bureau's  laboratory, 
for  the  identification  of  the  various  components  of  such  mixtures 
as  those  mentioned  depends  on  the  fact  that  the  different  components 
differ  in  specific  gravity.  This  method,  which  has  been  described 
in  Technical  Paper  78 a  of  the  bureau,  is  briefly  summarized  here. 
The  separation  is  effected  in  a  mixture  of  bromoform  (specific  grav- 
ity 2.83)  and  chloroform  (specific  gravity  1.49).  These  liquids  are 
miscible  in  all  proportions,  and  yield  liquid  mixtures  of  any  desired 
density  between  the  limits  of  their  respective  specific  gravities.  The 
various  salts  used  in  blasting  explosives  are  insoluble  in  such  mix- 
tures, and  the  specific  gravities  of  these  salts  lie  mostly  between 
1.50  and  2.50,  a  range  which  is  entirely  covered  by  the  possible 
bromoform-chloroform  mixtures. 

0  Storm,  C.  G.,  and  Hyde,  A.  L..  Specific-gravity  separation  applied  to  the  analysis  of 
mining  explosives  :  Tech.  Paper  78,  Bureau  of  Mines,  1914,  14  pp. 


QUALITATIVE   ANALYSIS. 


19 


A  series  of  these  liquid  mixtures  is  prepared,  with  specific  gravi- 
ties of  1.60,  1.77,  1.89,  1.98,  2.16,  etc.,  respectively.  The  specific 
gravities  mentioned  have  been  found  especially  useful,  but  obviously 
?ny  desired  mixture  within  the  limits  mentioned  may  be  prepared. 
These  mixtures  can  be  used  repeatedly,  being  filtered  back  into  the 
original  bottles  after  use.  Their  specific  gravities  should  be  checked 
from  time  to  time. 

A  sample  of  the  original  explosive  to  be  tested  is  extracted  several 
times  with  ether  to  remove  all  liquid  ingredients,  dried  thoroughly 
in  an  oven,  and  then  some  of  the  dry  material  is  shaken  with 
a  quantity  of  one  of  the  bromoform-chloroform  mixtures  in  a  small 
separatory  funnel  provided  with  a  wide-bore  stopcock.  On  standing 
a  short  time,  the  mixture  being  carefully  stirred  meanwhile  with  a 
thin  glass  rod  so  as  to  liberate  any  entangled  air  bubbles,  the  solid 
substances  separate  into  two  layers,  the  heavier  crystals  settling 
to  the  bottom  and  the  lighter  crystals  and  carbonaceous  material 
collecting  as  a  layer  in  the  upper  part  of  the  liquid. 

The  heavier  salt  may  be  drawn  off  into  a  dish  or  beaker  by  quickly 
opening  the  cock  and  again  closing  it  before  the  lighter  solids  begin 
to  come  through.  The  greater  part  of  the  liquid  drawn  off  is  de- 
canted back  into  the  funnel,  and  the  heavy  crystals  dried  and  ex- 
amined by  means  of  qualitative  tests. 

It  may  also  be  found  possible  to  separate  a  part  of  the  lighter  salt 
from  the  carbonaceous  material  by  further  treatment  in  a  similar 
manner  with  a  liquid  of  less  density  than  the  one  first  used. 

The  specific  gravities  of  some  of  the  more  common  salts  that  may 
be  present  are  as  follows:0 

Specific  gravities  of  salts  occurring  in  explosives. 


Salt. 

Speci'c 

gravity. 

Temier- 
ature. 

Authority. 

Ammonium  al"m  (crystals) 

1.62 

•c. 

Clarke.  F  W 

1.52 

Schroder 

1.74 

Do. 

Ammonium  perchlorate 

1.87 

Woulf 

Ammonium  sulphate 

1  77 

20 

Kettrers 

Barium,  nitrate                                                                        

3.23 

Clarke,  F.  W. 

Calcium  carbonate  (precipitated)                                       .  . 

2.72 

Rose  G 

2.97 

Schroder. 

Calcium  sulphate-f  2H2O 

2.32 

Clarke  F.  W. 

Ma^nesirm  carbonate 

3.04 

Schroder 

Magnesium  sulphate+THjO                                                 

1.68 

Clarke,  F.  W. 

Magnesium  sulphate  (anhydrous) 

2.65 

Do. 

5.03 

Retgers 

Potassium  alum  (crystals) 

1.75 

17 

Do. 

Potassium  chlorate  * 

2.33 

Clarke  F.  W. 

Potassium  chloride                                                     

1.99 

16 

Retgers. 

Potassium  nitrate                                                                     

2.09 

Clarke.  F.  W. 

Potassium  perchlorate 

2.52 

Schroder. 

Potassium  sulphate                                                      

2.66 

20 

Tutton. 

Sodium  chloride 

2.17 

17 

Retgers. 

Sodium  nitrate 

2.26 

Clarke  F.  W. 

Sodium  sulphate  (anhvdrous)                                   ...'.  

2.66 

Do. 

Sodium  sulphate+lOJB^O 

1.46 

Do. 

a  Landolt  and  Bornstein,  Physikalisch-chemische  Tabellen,  pp.  230-251. 


20  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

It  is  necessary  that  the  specific  gravity  of  the  liquid  mixture  used 
should  be  at  least  about  0.1  less  than  that  of  the  salt  which  it  is  de- 
sired to  separate  from  lighter  ingredients.  The  separation  is  never 
complete  because  of  the  buoyant  effect  of  air  bubbles  and  of  particles 
of  wood  pulp  or  other  carbonaceous  materials,  which  adhere  to  the 
heavier  crystals. 

EXAMPLE  OF  USEFULNESS  OF  METHOD. 

The  following  is  an  example  of  the  usefulness  of  the  method  of 
specific-gravity  separation  as  applied  to  an  ordinary  type  of  per- 
missible explosive:  The  solution  from  treatment  of  the  explosive 
with  water  was  found  by  the  usual  qualitative  tests  to  contain  NH4, 
Na,  NO3,  and  Cl.  Qualitative  and  quantitative  determinations  failed 
to  show  the  manner  in  which  the  acid  and  basic  radicles  were  com- 
bined, that  is,  whether  the  salts  present  were  NaNO3  and  NH4C1, 
NaCl,  and  NH4NO3,  or  a  mixture  of  all  four  of  these  substances. 
On  applying  the  specific-gravity  method,  using  a  liquid  mixture  of 
1.8  specific  gravity,  crystals  of  NaNO3  sank  to  the  bottom,  were 
drawn  off,  and  identified.  NaCl,  if  present,  would  have  been  found 
with  the  NaNO3,  but  no  test  for  Cl  was  obtained.  The  lighter  por- 
tion of  the  salts  gave  strong  qualitative  tests  for  NH4,  Cl,  and  NO3. 
It  was  therefore  established  that  the  explosive  contained  a  mixture 
of  NaNQ3,  NH4NO3,  and  NH4C1. 

MICROSCOPIC  EXAMINATION. 

The  use  of  the  microscope  in  identifying  constituents  of  the  in- 
soluble residue  is  discussed  on  page  74. 

Much  information  is  frequently  obtained  as  to  the  identity  of  the 
constituents  of  an  explosive  by  examining  a  sample  of  the  original 
explosive  under  relatively  low  magnification  by  the  aid  of  the  bin- 
ocular microscope.  In  some  explosives  it  is  possible  to  identify  as 
many  as  four  or  five  constituents  by  a  rapid  examination  under  the 
microscope.  Familiarity  with  the  form  and  appearance  of  the 
various  crystalline  and  noncrystalline  substances  used  in  explosives 
is,  of  course,  essential,  and  such  familiarity  can  best  be  obtained  by 
a  study,  under  the  microscope,  of  samples  of  these  different  sub- 
stances. 

Single  fragments  of  crystals  may  be  dissolved  in  a  drop  of  water 
and  the  solution  allowed  to  evaporate  slowly  on  a  microscope  slide, 
in  order  to  obtain  perfectly  formed  crystals  of  the  substance  to  be 
identified. 


QUANTITATIVE   ANALYSIS.  21 

QUANTITATIVE  ANALYSIS. 

It  has  been  shown  in  the  discussion  of  the  general  characteristics 
of  permissible  explosives  of  the  different  classes  (pp.  7  to  10)  that 
most  of  the  ingredients  used  in  the  explosives  of  any  class  may  be 
found  in  the  explosives  of  any  other  class.  A  separate  discussion  of 
the  methods  of  analysis  used  for  explosives  of  each  class  would  there- 
fore involve  much  useless  repetition.  In  general,  the  analysis  of 
any  permissible  explosive  is  carried  out  by  successive  extractions  of  a 
suitable  sample  of  the  explosive  with  different  solvents,  usually  ether, 
water,  dilute  hydrochloric  acid,  or  other  liquids  which  act  as  solvents 
only,  each  of  the  solutions  obtained  being  designed  to  contain  one 
or  more  unchanged  components  of  the  explosive.  The  components 
thus  separated  from  the  mixture  are  then  analyzed  to  determine  the 
proportion  of  each  in  the  explosive. 

The  general  method  of  procedure  is  therefore  quite  similar  to  that 
employed  in  the  analysis  of  the  ordinary  types  of  dynamite,  de- 
scribed in  Bulletin  51,a  although  the  introduction  of  components  not 
found  in  ordinary  dynamites  increases  the  difficulties  of  analyzing 
explosives  of  the  permissible  type. 

DETERMINATION   OF   MOISTURE. 

The  amount  of  moisture  in  ammonium-nitrate  explosives  is  usu- 
ally small.  Obviously,  water  is  never  intentionally  added  to  explo- 
sives of  this  type  for  the  purpose  of  reducing  the  temperature  of  ex- 
plosion. Because  of  the  hygroscopic  nature  of  ammonium  nitrate, 
and  the  fact  that  its  insensitiveness  is  increased  by  the  absorption  of 
moisture,  all  ingredients  of  explosives  containing  ammonium  nitrate 
are  generally  well  dried.  About  75  per  cent  of  the  explosives  of  this 
type  tested  by  the  bureau  have  contained  less  than  1  per  cent  of  mois- 
ture. 

The  moisture  content  of  the  nitroglycerin  explosives  may  be  rather 
high,  as  the  addition  of  water  is  one  of  the  means  frequently  em- 
ployed for  reducing  the  flame  temperature  of  such  explosives.  The 
moisture  content  of  some  of  the  permissible  explosives  of  this  type  is 
as  high  as  10  per  cent. 

The  determination  of  moisture  in  permissible  explosives  of  all 
classes  is  made  by  the  method  described  in  Bulletin  51.6  A  sample 
weighing  approximately  2  grams  is  spread  evenly  over  the  surface 
of  a  2-inch  watch  glass  and  desiccated  over  sulphuric  acid  for  three 
days  at  a  room  temperature  as  near  20°  C.  as  possible.  The  loss  of 
weight  is  considered  as  moisture. 

a  Snelling,  W.  O.,  and  Stoyn,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  16-50. 

6  Snelling,  W.  O.,  and  Storm,  C.  G.,  op.  cit.,  p.  29. 


22  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

FACTORS  AFFECTING  RESULTS  OF  MOISTURE  DETERMINATION. 

The  extent  to  which  these  results  are  affected  by  variations  in  tem- 
perature, weight  of  sample,  exposed  surface  of  sample,  quantity  and 
strength  of  acid,  type  of  desiccator,  and  other  conditions  have  been 
considered  in  Bulletin  51.° 

The  accuracy  of  the  results  obtained  in  determining  moisture  by 
desiccation  also  depends  on  the  absence  of  any  other  ingredients  from 
the  explosive  that  could  be  lost  during  desiccation. 

The  principal  ingredients  whose  volatility  may  influence  the  results 
are  nitroglycerin,  some  of  the  nitrosubstitution  compounds,  and  com- 
bined water  in  substances  containing  water  of  crystallization. 

EFFECT  OF  VOLATILITY  OF  NITROGLYCERIN. 

It  has  been  demonstrated  by  experiments  described  in  Bulletin  5P 
that  there  is  a  continual  loss  of  nitroglycerin  from  explosives  con- 
taining this  ingredient,  during  the  determination  of  moisture  by 
desiccation ;  that  this  loss  varies  with  the  temperature ;  and  that  it  is 
impossible  to  bring  such  a  sample  to  constant  weight  under  ordinary 
conditions  of  determination. 

It  is  believed,  however,  that  in  desiccation  for  three  days  under  the 
conditions  above  described  the  amount  of  nitroglycerin  volatilized  is 
inappreciable. 

ILLUSTRATIVE  EXPEEIMENT. 

To  illustrate  the  fact  that  nitroglycerin  is  appreciably  volatile  at 
ordinary  temperatures  and  that  its  volatility  increases  with  the  tem- 
perature, an  experiment  was  described  in  Bulletin  51e  in  which  2 
grams  of  a  "  60  per  cent "  dynamite  was  spread  on  a  3-inch  watch 
glass,  dried  over  sulphuric  acid  for  three  days  to  remove  moisture, 
and  then  placed  in  an  empty  desiccator  containing  no  drying  agent, 
the  desiccator  being  placed  in  an  incubator  oven  at  a  constant  tem- 
perature of  33°  to  35°  C.  The  sample  was  weighed  at  intervals  and 
the  loss  of  weight  noted.  The  results  are  shown  by  the  curve  in 
figure  1. 

Since  the  publication  of  the  bulletin  mentioned  additional  weigh- 
ings of  the  sample  have  been  made,  covering  a  total  period  of  459 
days.  After  the  last  weight  was  taken  the  sample  on  the  watch  glass 
was  analyzed  in  order  to  determine  whether  the  total  loss  of  weight 
could  be  accounted  for  by  the  actual  loss  of  nitroglycerin  as  deter- 
mined by  analysis. 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite  :  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  19-27. 

6  Snelling,  W.  O.,  and  Storm,  C.  G.,  op.  cit.,  pp.  24-20*         • 
e  Snelling,  W.  O.,  and  Storm,  C.  G.,  op  cit.,  pp.  26,  27. 


QUANTITATIVE  ANALYSIS.  23 

The  entire  data  of  the  experiment  are  shown  in  the  following  table : 

Effect  of  heating  "  60  per  cent "  dynamite  in  an  empty  desiccator  at  33°   to 

35°  C.  for  459  days. 


Time  in 
desiccator. 

Loss  of 
weight- 

Time  in 
desiccator. 

Loss  of 
weight. 

Days. 

Per  cent. 

Days. 

Per  cent. 

4 

0.13 

77 

5.35 

7 

.46 

202 

9.33 

10 

.80 

243 

11.13 

13 

1.10 

331 

13.32 

16 

1.40 

418 

16.75 

20 

1.75 

459 

17.52 

41 

3.40 

The  weight  of  the  dried  sample  at  the  time  of  beginning  the  heat- 
ing in  the  empty  desiccator  was  1.9720  grams ;  its  final  weight  after 


O   2 


12 


18 


?A 


30 


!6          42 
DAYS 


48 


54 


78 


FIGURE  1. — Result  of  exposing  dry  "  60  per  cent "  dynamite  for  77  days  in  desiccator  at 
33°  to  35°  C.  without  desiccating  agent. 

459  days'  heating  was  1.6265  grams,  a  total  loss  of  0.3455  gram.  The 
original  dry  sample  contained  60.26  per  cent,  or  1.1883  grams,  of 
nitroglycerin,  whereas  after  heating  for  459  days,  only  0.8355  gram 
of  nitroglycerin  was  found  by  analysis,  showing  a  loss  of  0.3528  gram 
of  nitroglycerin.  This  figure  agrees  fairly  well  with  the  actual  loss 
of  weight,  0.3455  gram. 

To  summarize  the  results  of  this  experiment,  about  one-third  of 
the  total  quantity  of  nitroglycerin  originally  present  was  lost  by 
exposure  to  a  temperature  of  33°  to  35°  C.  for  459  days.  The  uni- 


24  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

f  ormity  of  the  rate  of  loss  is  indicated  by  the  curve  in  figure  2.  Com- 
plete analysis  of  the  sample  showed  that  no  change  other  than  loss  of 
nitroglycerin  had  occurred. 

There  is  no  doubt  that  the  loss  of  nitroglycerin  was  due  to  vola- 
tilization and  not  to  decomposition.  On  several  occasions  when  the 
desiccator  was  opened  to  weigh  the  sample,  a  piece  of  potassium 
iodide-starch  paper  was  at  once  exposed  to  the  atmosphere  within 
the  desiccator,  but  in  no  case  was  any  reaction  for  oxides  of  nitrogen 
obtained,  nor  could  any  odor  of  decomposition  products  be  detected. 

After  the  completion  of  the  experiment  the  interior  walls  of  the 
empty  desiccator  were  washed  with  sulphuric  acid  and  this  acid 
transferred  to  the  nitrometer  in  order  to  test  it  for  the  presence  of 
nitroglycerin.  A  small  amount  of  NO  generated  (insufficient  for  a 
reading)  indicated  the  presence  of  nitroglycerin  on  the  walls  of  the 


16 


12 


50 


100 


150 


200  250  300 

TIME,  DAYS 


•350 


400 


450 


500 


FIGURE  2. — Results  of  exposing  "  60  per  cent "  dynamite  for  459  days  in  desiccator  at 
33°  to  35°  C.  without  desiccating  agent. 

desiccator,  but  most  of  the  nitroglycerin  volatilized  from  the  dyna- 
mite sample  had  apparently  escaped  from  the  desiccator. 

EFFECT  OF  VOLATILITY  OF  NITROTOLUENES. 

The  volatility  of  certain  of  the  nitrosubstitution  compounds  may 
also  have  some  effect  on  the  results  of  the  determination  of  moisture 
by  desiccation.  In  order  to  investigate  this  point  experiments  were 
made  on  the  more  commonly  used  nitrotoluenes.  The  samples  were 
desiccated  over  sulphuric  acid  for  a  number  of  days  and  the  loss  of 
weight  noted  at  intervals. 

The  nitrotoluenes  used  for  the  tests  were  of  the  grade  generally 
used  in  blasting  explosives  in  this  country.  The  "liquid"  dinitro- 
toluenes  and  trinitroluenes  are  mixtures  containing  chiefly  dinitro- 
toluenes  and  trinitrotoluenes,  with  more  or  less  mononitrotoluene. 
Sample  A,  "  liquid  trinitrotoluene,"  contained  only  a  trace  of  mono 


QUANTITATIVE   ANALYSIS. 


25 


compound,  sample  C,  "liquid  dinitrotoluene,"  contained  11.36  per 
cent  of  mono  compound. 


VOLATILITY   OVER    SULPHURIC    ACID   IN    ORDINARY   DESICCATORS. 


The  results  of  these  experiments  are  given  in  the  following  tables. 
Similar  samples  are  uniformly  designated  by  letter,  as  A,  B,  C, 
throughout  the  tables  and  descriptions  of  tests : 

Volatility  of  nitrotoluenes  in  desiccators  in  presence  of  sulphuric  acid. 

(Samples  spread  on  watch  glasses). 


Designa- 

Test 

Original 

Lo 

ss  in  weigl 

it  after  des 

iccation  fo: 

•— 

sample.o 

No. 

sample. 

Iday. 

3  days. 

4  days. 

7  days. 

11  days. 

Mononitro  toluene  (ortho). 
Do 

G 
G 

1 
2 

Grams. 
3.72 
8.31 

Or  am. 
0.  0405 
.0341 

Oram. 
0.0766 
.0656 

Oram. 
0.  1521 
.1197 

Oram. 
0.2225 
.3091 

Gram. 
0.2834 
.5426 

Dinitrotoluene  (crystals), 
melting  point  66°  to  68° 

F 

3 

1.00 

.0014 

.0015 

.0030 

.0004 

Trinitrotoluene  (crystals), 
melting  point  81°  to  82° 

Q 

E 

4 

1  00 

0010 

0010 

"Liquid  dinitrotoluene  "b 
Do 

C 

c 

5 

6 

5.73 
6.56 

.0082 
.0085 

.0203 
.0212 

.0279 
.0268 

.0548 
.0512 

.0864 
.0818 

"Liquid  trinitrotoluene"  c 

A 

7 

1  8539 

0033 

0037 

.0050 

.0060 

a  Uniform  throughout  this  and  other  tables. 

&  Commercial  designation.    Substance  contains  a  trace  of  mononitrotoluene. 

c  Contains  11.36  per  cent  mononitrotoluene. 

The  results  show  that  crystalline  trinitrotoluene  does  not  volatilize 
appreciably  on  desiccating;  that  crystalline  dinitrotoluene  is  very 
slightly  volatile,  but  the  loss  in  three  days  is  negligible;  and  that 
mononitrotoluene  (ortho),  on  the  other  hand,  is  appreciably  volatile, 
so  that  its  presence  in  an  explosive  would  introduce  an  error  in  the 
determination  of  moisture.  The  slight  volatility  of  the  liquid  tri- 
nitrotoluene, and  the  considerably  greater  volatility  of  the  liquid 
dinitrotoluene,  are  probably  largely  due  to  the  content  of  mono- 
nitrotoluene in  each. 

EFFECT   OF    SURFACE   ABEA   OF    SAMPLE   ON   VOLATILITY   OF    NITROTOLUENES. 

The  effect  of  the  surface  area  of  the  sample  exposed  in  the  desic- 
cator was  shown  in  the  case  of  the  liquid  nitrotoluenes  by  distribut- 
ing each  sample  over  a  layer  of  sand  spread  uniformly  on  a  jeatch 
glass. 

In  the  following  determinations  approximately  10  grams  of  dry 
(60-mesh)  sand  was  spread  on  each  watch  glass  and  approximately 
3  grams  of  the  liquid  sample  allowed  to  drop  onto  the  sand  so  that 
it  was  entirely  moistened,  but  no  accumulations  of  liquid  were  visible. 
The  watch  glasses  were  then  placed  in  separate  desiccators  over 
sulphuric  acid  and  weighed  at  intervals  of  two  days. 


26 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


Results  of  desiccation  of  liquid  nitrotoluenes. 
[Samples  distributed  over  sand  and  placed  in  desiccators  over  sulphuric  acid.] 


Sample. 

Sample 
No.a 

Test 
No. 

Original 
weight  of 
sample. 

Loss  in  weight  after  desiccation  for— 

2  days. 

4  days. 

6  days. 

8  days. 

Mononitro  toluene  (ortho).  .  . 

G 
G 
C 
C 
A 
A 

1 
2 
3 
4 
5 
7 

Grams. 
3.3767 
2.  9936 
3.  6967 
3.0982 
3.2256 
3.3519 

Gram. 
0.  1793 
.1745 
.0276 
.0281 
.0071 
.0064 

Gram. 
0.  3138 
.3725 
.0530 
.0531 
.0143 
.0137 

Gram. 
0.  4303 
.4849 
.0830 
.0754 
.0161 
.0159 

Gram. 
0.  5421 
.5840 
.1096 
.0984 
.0225 
.0214 

Do 

Dinitro  toluene  ("liquid").  .. 
Do  . 

Trinitrotoluene  ("liquid").  .  . 

Do  

a  Uniform  throughout  this  and  other  tables. 

These  results  show  that  with  an  increase  in  the  surface  of  the  liquid 
exposed  in  the  desiccator  the  rate  of  loss  increases. 

VOLATILITY   OVER   SULPHURIC   ACID   IN   VACUUM    DESICCATORS. 

The  volatility  of  nitrotoluenes  when  exposed  in  vacuum  desiccators 
containing  sulphuric  acid  was  also  investigated.  Experiments  were 
made  on  both  crystalline  and  liquid  dinitrotoluenes  and  trinitroto- 
luenes, but  not  on  mononitrotoluene,  there  being  no  doubt  in  regard 
to  the  ready  volatility  of  mononitrotoluene  in  a  vacuum. 

Samples  of  1  gram  each  were  weighed  in  small  low-form  beakers, 
and  each  beaker  was  placed  in  a  separate  Hempel  vacuum  desiccator 
containing  fresh  sulphuric  acid.  The  sample  of  "liquid  dinitroto- 
luene"  (C)  contained  11.36  per  cent  mononitrotoluene,  the  sample  of 
"liquid  trinitrotoluene"  (B)  contained  2.33  per  cent  mononitroto- 
luene, whereas  the  "  liquid  trinitrotoluene "  (A)  contained  only  a 
trace  of  mono  compound.  At  intervals,  as  indicated  in  the  table,  the 
vacuum  was  relieved  and  the  samples  weighed. 

The  results  were  as  follows : 

Loss  of  iveight  of  nitroluenes  in  vacuum  desiccators. 

[Quantity  of  sample  taken  for  analysis,  1  gram.] 


Time  sample  was  exposed. 

Loss  in  weight. 

Trinitro- 
toluene a 
(crystals) 
(E). 

Trinitro- 
toluene 
("liquid") 
(A). 

Trinitro- 
toluene 
("liquid") 
(B). 

Dinitro- 
toluene 
("liquid") 
'     (C). 

Dinitro- 
toluene  & 
(crystals) 
(F). 

Days. 
1             

Gram. 
0.  0007 
.0007 
.0007 

Gram. 
0.0020 
.0050 
.0076 
.0082 
.0093 
.0105 
.0125 
.0135 
.0140 
.0145 
.0150 
.0155 

Gram. 
0.  0050 
.0104 
.0174 
.0198 
.0225 
.0253 
.0289 
.0300 
.0318 
.0330 
.0339 
.0363 

Gram. 
0.0199 
.0471 
.0831 
.0939 
.1023 
.1076 
.1161 
.1182 
.1216 
.1240 
.1260 
.1290 

Gram. 
0.0028 
.0064 
.0074 
.0095 
.0112 
.0126 
'  .0152 
.0188 
.0205 
.0225 
.0241 
.0256 

2 

4   .           

5 

6  

7 

9  

10  

11... 

12  

13  

14  

Melting  point,  81°  to  82°  C. 


6  Melting  point,  66°  to  68°  C. 


QUANTITATIVE   ANALYSIS. 


27 


The  fact  that  the  loss  from  pure  crystalline  trinitrotoluene  is  no 
greater  than  its  probable  moisture  content,  and  that  pure  dinitrotolu- 
ene  undergoes  only  a  slight  volatilization,  whereas  the  loss  in  the  case 
of  the  liquid  materials  is  greater  as  the  known  content  of  mono- 
nitrotoluene  is  greater,  indicates  that  the  volatility  of  the  "liquid 
nitrotoluenes  "  is  due  partly  to  loss  of  mononitrotoluene  and  partly 
to  loss  of  dinitrotoluene.  These  results  confirm  the  results  of  desic- 
cation in  ordinary  desiccators. 

After  the  14  days'  desiccation  the  samples  of  liquids  were  again 
examined  for  mononitrotoluene  with  the  following  results:  "Liquid 
trinitrotoluene"  (A),  none;  "liquid  trinitrotoluene"  (B),  0.83  per 
cent;  "liquid  dinitrotoluene"  (C),  1.39  per  cent. 

As  a  further  point  of  interest  the  above  vacuum-desiccation 
experiments  were  repeated  on  the  "liquid  trinitrotoluene"  (B)  and 
on  the  "liquid  dinitrotoluene"  (C),  in  order  to  determine  whether 
the  mononitrotoluene  could  be  entirely  removed  from  them  by  con- 
tinued treatment. 

The  results  of  these  tests  are  shown  in  the  table  following. 

Loss  of  weight  of  "  liquid  nitrotoluenes  "  in  vacuum  desiccators. 
[Quantity  taken  for  analysis,  1  gram.] 


Period 
of  ex- 
posure. 

Loss  in  weight. 

Period 
of  ex- 
posure. 

Loss  in  weight. 

Trinitrotoluene 
(liquid). 
(B). 

Dinitrotoluene 
(liquid). 
(C). 

Trinitrotoluene 
(liquid). 
(B). 

Dinitrotoluene 
(liquid). 
(C). 

Days. 
I 

Gram. 
0.0022 
.0044 
.0095 
.0132 
.0187 
.0208 
.0238 
.0272 

Per  cent. 
0.22 
.44 
.95 
1.32 
1.87 
2.08 
2.38 
2.72 

Gram. 
0.  0159 
0382 
0623 
0829 
1036 
1080 
1156 
1209 

Per  cent. 
1.59 
3.82 
6.23 
8.29 
10.36 
10.80 
11.56 
12.09 

Days. 
17 

Gram. 
0.0297 
.0317 
.0360 
.0432 
.0448 
.0474 
.0504 

Per  cent. 
2.97 
3.17 
3.60 
4.32 
4.48 
4.74 
5.04 

Gram. 
0.  1251 
.1298 
.1348 
.1414 
.1434 
.1461 
.1502 

Per  cent. 
12.51 
12.98 
13.44 
14.18 
14.34 
14.61 
15.02 

3 

19  

5 

21  
25  
27  
29  
31  

7  

10 

11 

13..      . 

15 

After  31  days  of  vacuum  desiccation  these  samples  were  found  to 
contain  no  mononitrotoluene.  The  total  loss  from  each  sample  was, 
however,  considerably  greater  than  the  amount  of  mononitrotoluene 
originally  present,  and,  furthermore,  the  fact  that  constant  weight  was 
not  obtained  even  after  all  of  the  mono  compound  had  volatilized 
indicated  a  slight  volatility  of  other  ingredients  of  these  liquid 
mixtures. 

The  curves  in  figure  3  indicate  graphically  the  rate  of  loss  of  each 
of  the  two  samples  tested. 

DETERMINATION  OF  MOISTURE  IN  EXPLOSIVES  CONTAINING  "  LIQUID  NITROTOLUENES." 

A  series  of  experiments  was  made  to  determine  the  extent  to  which 
the  results  of  the  usual  methods  for  determining  moisture  in  explo- 
sives are  affected  by  the  presence  of  the  more  or  less  volatile  "  liquid 


28 


ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 


nitrotoluenes."  For  this  investigation  a  large  sample  (about  250 
grams)  of  ordinary  45  per  cent  nitroglycerin  dynamite  was  thor- 
oughly mixed  in  a  large  porcelain  dish  and  divided  into  five  50-gram 
parts,  each  of  which  was  placed  in  a  smaller  porcelain  dish.  These 
five  samples  were  then  treated  as  follows : 

1.  Five  grams  of  mononitrotoluene   (ortho)   was  added,  drop  by 
drop,  to  sample  1  in  such  a  manner  as  to  distribute  it  through  the 
sample  as  thoroughly  as  possible.    The  sample  was  then  well  mixed 
with  a  porcelain  spoon  and  placed  in  a  bottle. 

2.  Five  grams  of  "liquid  dinitrotoluene "  (C),  with  a  mononitro- 
toluene content  of  about  11  per  cent,  was  added  to  sample  2  in  the 
manner  described  for  sample  1. 


15 

TIME,  DAYS 

FIGURE  3.— Result  of  exposure  of  "  liquid  nitrotoluenes  "  in  vacuum  desiccators. 

3.  Five  grams  of  "liquid  dinitrotoluene"  (D),  with  a  mononitro- 
toluene content  of  about  4  per  cent,  was  added  as  described  above. 

4.  Five  grams  of  "liquid  trinitrotoluene"   (A),  practically  free 
from  mononitrotoluene,  was  added  as  described  above. 

5.  No  addition  was  made  to  sample  5,  but  it  was  mixed  in  the  same 
manner  as  the  other  samples,  so  that  the  exposure  to  the  atmosphere 
would  be  the  same  in  each  test.    This  sample  was  used  for  comparison 
with  samples  1  to  4. 

Moisture  determinations  were  then  made  on  each  of  these  five 
samples  (1)  by  desiccating  over  sulphuric  acid  in  ordinary  desic- 
cators and  (2)  by  desiccating  over  sulphuric  acid  in  Hemple  vacuum 
desiccators.  The  weight  of  the  sample  used  for  the  determinations 
was  2.2  grams  for  samples  1  to  4,  inclusive,  and  2  grams  for  sample 
5 ;  samples  1  to  4  contained  0.1  gram  of  nitro  compound  for  each 
gram  of  the  dynamite.  It  was  therefore  assumed  that  any  loss  of 
weight  in  samples  1  to  4  greater  than  that  of  sample  5  was  due  to 
volatility  of  the  nitro  compounds.  Each  sample  was  placed  in  a 
separate  desiccator. 


QUANTITATIVE  ANALYSIS. 

The  results  of  the  determinations  were  as  follows : 


29 


Loss  in  weight  of  "liquid  nitrotoluenes"  on  desiccation  over  H2SOi  in  ordinary 

desiccators. 


Sample  No. 

Loss  in  weight  after  desicca- 
tion for— 

Sample  No. 

Loss  in  weight  after  desicca- 
tion for— 

3  days. 

4  days. 

6  days. 

3  days. 

4  days. 

6  days. 

1 

Gram. 
0.0795 
.0405 
.0400 

Gram. 
0.0860 
.0430 
.0400 

Gram. 
0.  1055 
.0486 
.0410 

4 

Gram. 
0.0400 
.0380 

Gram. 
0.0400 
.0390 

Gram. 
0.0405 
.0410 

2 

5  

3             

Loss  in  weight  of  "liquid  nitrotoluenes"  on  desiccation  over  H2SO*  in  Hempel 

vacuum  desiccators. 


Sample 
No. 

Loss  in  weight  after  desiccation  for— 

Sample 
No. 

Loss  in  weight  after  desiccation  for— 

Iday. 

2  days. 

3  days. 

4  days. 

6  days. 

Iday. 

2  days. 

3  days. 

4  days. 

6  days. 

1 

Gram. 
0.1185 
.0450 
.0480 

Gram. 
0.  1915 
.0545 
.0550 

Gram 
0.  2255 
.0620 
.0590 

Gram. 
0.2410 
.0685 
.0620 

Gram. 
0.2530 
.0733 
.0710 

4... 

Gram. 
0.0392 
.0380 

Gram. 
0.0422 
.0410 

Gram. 
0.0442 
.0440 

Gram. 
0.0457 
.0475 

Gram. 
0.0472 
.0514 

2 

5 

3 

These  results  show  plainly  that  orthonitrotoluene  is  readily  lost 
from  explosives  during  the  ordinary  determination  of  moisture, 
causing  the  results  to  be  abnormally  high.  In  three  days'  desicca- 
tion in  an  ordinary  desiccator,  the  loss  of  orthonitrotoluene  was 
about  equal  to  the  amount  of  moisture  present  in  the  sample,  and 
in  four  to  six  days'  desiccation  in  vacuum,  the  total  loss  was  equal 
to  the  sum  of  the  actual  amounts  of  moisture  and  orthonitrotoluene 
present. 

The  liquid  dinitrotoluenes  do  not  appreciably  affect  the  result  of 
i  the  moisture  determination  in  ordinary  desiccators.  In  vacuum 
'  desiccators  the  error  is  small  if  the  weighing  is  made  at  the  end  of 
I  24  hours,  whereas  for  longer  periods  of  desiccation  the  loss  increases 
gradually,  and  is  greater  as  the  content  of  mononitrotoluene  in  the 
I  "  liquid  dinitrotoluene  "  is  greater. 

"  Liquid  trinitrotoluene  "  does  not  affect  the  results  in  either  ordi- 
nary or  vacuum  desiccators. 

These  determinations  confirm  the  results  obtained  by  desiccation 
of  the  nitrotoluenes  alone,  but  are  considered  as  indicating  more 
exactly  the  behavior  of  these  ingredients  in  explosives  and  their 
actual  influence  on  the  results  of  the  moisture  determination. 

EFFECT  OF  VOLATILITY  OF  MONONITROBENZENE. 

Mononitrobenzene  is  seldom  used  in  blasting  explosives  because 
of  its  high  degree  of  volatility;  in  fact,  it  is  a  constituent  of  only 
one  of  the  explosives  now  on  the  "permissible"  list,  and  in  this 
10293°— Bull.  96—16 3 


30 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


explosive  is  present  in  very  small  quantity.  That  its  presence  in 
an  explosive  would  seriously  affect  the  results  of  the  moisture  deter- 
mination was  shown  by  the  following  experiments : 

Ten  grams  of  mononitrobenzene  that  was  exposed  on  a  3-inch 
watch  glass  in  an  ordinary  sulphuric-acid  desiccator  lost  0.317  gram 
in  1  day,  0.702  gram  in  3  days,  and  2.543  grams  in  10  days. 

A  similar  sample  that  was  desiccated  over  CaCl,  lost  0.092  gram 
in  1  day,  0.197  gram  in  3  days,  and  0.386  gram  in  10  days. 

A  sample  distributed  over  sand  on  a  watch  glass  and  exposed  for 
10  days  over  sulphuric  acid  lost  about  40  per  cent  in  weight,  and 
over  calcium  chloride  about  20  per  cent. 

In  a  vacuum  desiccator  with  sulphuric  acid  mononitrobenzene  was 
completely  volatilized,  10  grams  on  a  watch  glass  evaporating  com- 
pletely in  10  days,  and  2.5  grams  spread  over  a  layer  of  sand  evapo- 
rating completely  in  3  days. 

EFFECT  OF  MATERIALS  CONTAINING  WATER  OF  CRYSTALLIZATION. 

Salts  containing  water  of  crystallization  effectually  prevent  any 
reliable  determination  of  moisture  by  the  usual  method  of  desicca- 
tion, because  all  of  such  salts  as  are  commonly  used  in  explosives 
lose  a  portion  of  their  water  of  crystallization  on  exposure  to  a  dry 
atmosphere,  and  it  is  impossible  to  differentiate  between  the  loss 
due  to  evaporation  of  hygroscopic  moisture  and  that  due  to  water 
of  crystallization. 

BESULTS   OF  TESTS    WITH   MAGNESIUM    SULPHATE   AND   POTASSIUM   ALUM. 

Tests  were  made  with  pure  crystallized  magnesium  sulphate  and 
potassium  alum  to  determine  whether  any  definite  proportion  of  the 
water  of  crystallization  would  be  removed  by  desiccation  over  either 
sulphuric  acid  or  calcium  chloride. 

The  percentage  loss  of  weight  according  to  the  number  of  mole- 
cules of  water  lost  should  be  as  follows : 

Theoretical  loss  of  weight  from  magnesium  sulphate  and  potassium  alum  for 
each  molecule  of  water  lost. 


Number  of  molecules  of  HjO 
lost. 

Theoretical  loss  in 
weight. 

Number  of  molecules  of  H2O 
lost. 

Theoretical  loss  in 
weight. 

KA1- 
(S04)2.- 
12H20. 

MgS04.- 
7H2O. 

KA1- 
(S04)2.- 
12H20. 

MgS04.- 
7H20. 

1 

Per  cent. 
3.79 
7.58 
11.37 
15.16 
18.95 
22.74 

Per  cent. 
7.30 
14.60 
21.90 
29.20 
36.50 
43.80 

7 

Per  cent. 
26.53 
30.32 
34  11 

Per  cent. 
51.10 

2  

8  

3 

9 

4     

10  7  . 

37.90 

5 

11  . 

41.69 

6 

12 

45.48 

QUANTITATIVE  ANALYSIS. 


31 


Samples  of  these  salts  were  ground  to  pass  a  20-mesh  sieve,  exposed 
on  watch  glasses  in  desiccators,  and  the  loss  of  weight  noted.  The 
results  were  as  follows: 

Loss  of  weight  from  magnesium  sulphate  and  potassium  alum  on  desiccation 
over  sulphuric  acid  and  calcium  chloride. 


Time  of  desiccation. 

Loss  of  weight. 

KA1(SO4)2.12H2O. 

MgSOi.7H20. 

Over  H2SO4. 

Over  CaCl2. 

Over  H2SO4. 

Over  CaCl2. 

Days. 
3                          

Per  cent. 
8.  68  to  9.  86 

Per  cent. 
3.  42  to   3.94 
13.  41  to  14.  96 

Per  cent. 
14.  15  to  14.  51 
25.  72  to  29.  11 

Per  cent. 
9.  32  to   9.87 
14.  71  to  18.  35 

g 

9 

28.  08  to  30.  84 

12 

17.  90  to  20.  05 

19.  77  to  20.  55 

DISCUSSION    OF    RESULTS    OF    EXPEEIMENTS. 

The  above  results  indicate  the  impossibility  of  correcting  the  total 
loss  of  weight  found  by  desiccating  an  explosive  containing  salts 
carrying  water  of  crystallization  for  the  amount  of  such  water  of 
crystallization  lost  by  a  given  treatment. 

Furthermore,  it  is  apparent  that  it  is  impossible  to  determine  the 
total  hygroscopic  moisture  plus  water  of  crystallization  by  drying  in 
an»  oven  at  temperatures  higher  than  atmospheric,  because  under  such 
conditions  other  ingredients,  such  as  nitroglycerin  and  ammonium 
nitrate,  would  be  more  or  less  volatilized. 

It  is  therefore  necessary  to  determine  all  constituents  other  than 
moisture  by  direct  methods  and  estimate  the  content  of  water  by 
difference.  In  other  words  the  remainder  obtained  by  deducting  the 
sum  of  all  constituents  other  than  water  from  100  per  cent  is  as- 
sumed to  be  the  total  water  content  of  the  explosive.  For  this  pur- 
pose the  constituent  to  which  the  water  of  crystallization  belongs 
may  be  calculated  as  containing  its  full  quota  of  water  of  crystalli- 
zation (for  example,  magnesium  sulphate  as  MgSO4.7H2O),  and  the 
difference  from  100  per  cent  reported  as  moisture,  or  the  crystallized 
salt  may  be  calculated  as  anhydrous  and  the  difference  reported  as 
water  of  crystallization  plus  moisture.  The  latter  method  is  prob- 
ably the  more  correct,  as  it  is  safe  to  assume  that  the  crystallized  salt 
has  undergone  some  loss  of  its  water  by  efflorescence  before  being 
incorporated  in  the  explosive  mixture. 

In  either  case  the  algebraic  sum  of  all  of  the  errors  in  the  determi- 
nations of  the  other  ingredients  of  the  explosive  is  thrown  on  the 
water  when  the  latter  is  taken  by  difference. 

In  many  cases  a  more  correct  value  for  the  actual  hygroscopic 
moisture  present  may  be  obtained  by  calculation,  assuming  certain 


32 


ANALYSIS  OF  PERMISSIBLE   EXPLOSIVES. 


average  values  for  the  percentage  of  moisture  present  in  the  various 
ingredients  of  the  mixture. 

The  average  values  for  the  moisture  content  of  the  chief  ingre- 
dients of  such  explosives,  according  to  the  general  practice  of  man- 
ufacturers in  this  country,  are  approximately  as  follows : 

Approximate  average  moisture  content  of  constituents  of  explosives. 

Per  cent. 

Nitroglycerin 0.  5 

Sodium    nitrate .5 

Ammonium    nitrate- .3 

Wood  pulp 5.0 

Corn   meal 12.0 

Wheat    flour 10.0 

If  these  values  be  assumed  to  be  correct,  and  the  proportion  of  each 
constituent  of  the  explosive  except  moisture  has  been  determined,  an 
approximation  to  the  moisture  content  of  the  explosive  may  be 
calculated.  The  following  table  shows,  for  a  number  of  explosives 
of  different  types  made  by  different  manufacturers,  a  comparison  of 
the  calculated  moisture  content  with  the  result  of  the  determination 
of  moisture  by  the  usual  desiccation  method,  and  with  that  obtained 
by  difference  from  100  per  cent,  as  proposed  above. 

Moisture  content  of  various  explosives,  as  obtained  by  desiccation,  by  difference, 

and  by  calculation. 


Sample 
No. 

Type  of  explosive^ 

Moisture  content. 

By  desic- 
cation. 

By  dif- 
ference. 

By  cal- 
culation. 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 

Dynamite  (40 
.  .  .do  

per  cent  strength) 

Per  cent. 
0.90 
.94 

Per  cent. 

Per  cent. 
0.93 
1.00 
.75 
.76 
.49 
.74 
2.41 
2.24 
1.05 
.41 
.25 
.97 
1.80 

NH4N03dyn£ 
do 

unite  (40  per  cent  strength) 

.92 

92 

Permissible  e> 
do 

:plosive  (N  H<N  O3  class)  ... 

.44 

.70 

Permissible  e> 
do 

cplosive  (hydrated  class)  .   . 

2.10 
2.25 
1.16 
.20 
.19 
.27 
1.00 

...do... 

do 

...do... 

.do 

do 

For  most  of  the  samples  the  calculated  result  agrees  quite  well  with 
the  results  by  desiccation  or  by  difference.  The  discrepancy  of  re- 
sults shown  by  samples  12  and  13  is  probably  due  to  the  fact  that  the 
crystallized  magnesium  sulphate  in  those  explosives  had  partly 
effloresced,  causing  the  moisture  determined  by  difference  to  be  too 
low.  Cases  have  been  noted  where  the  same  cause  resulted  in  a  nega- 
tive value  for  "  moisture  by  difference."  The  only  feasible  manner 
of  reporting  the  analysis  of  such  explosives  is  to  calculate  the  crys- 


QUANTITATIVE   ANALYSIS.  33 

tallized  ingredient  as  anhydrous  and  estimate  by  difference  the  com- 
bined moisture  and  water  of  crystallization. 

EXTRACTION    WITH   ETHER. 

It  has  been  indicated  on  page  13  that  the  principal  substances  that 
may  be  found  in  the  ether  extracts  of  permissible  explosives  are 
nitroglycerin,  nitropolyglycerin,  various  nitrosubstitution  compounds, 
sulphur,  oils,  vaseline  or  paraffin,  and  resins.  Small  amounts  of  oils 
and  resins  extracted  from  the  wood  pulp  or  cereal  products  in  per- 
missible explosives  are,  as  in  the  ordinary  types  of  dynamites,  gen- 
erally found  in  the  ether  extract,  in  addition  to  materials  of  similar 
nature  that  may  constitute  actual  ingredients  of  the  explosive. 

METHOD   OF  EXTRACTION. 

The  removal  of  ether-soluble  ingredients  from  all  permissible  ex- 
plosives is  carried  out  according  to  the  general  method  employed  for 
dynamites.*  Samples  of  6  to  10  grams  of  the  explosive  in  its  origi- 
nal condition  are  weighed  in  Gooch  crucibles  with  asbestos  mats  or 
in  suitable  porous  filtering  crucibles,  and  extracted  with  ether  in  a 
Wiley  extractor  or  other  convenient  form  of  reflux-condenser  extrac- 
tion apparatus. 

The  extraction  with  ether  usually  requires  about  three-quarters  of 
an  hour,  but  it  is  always  advisable  to  insure  that  extraction  is  com- 
plete by  evaporating  a  small  quantity  of  the  ether  passing  through 
the  crucible.  If  the  ether  completely  evaporates,  leaving  no  residue, 
the  extraction  is  complete. 

The  crucibles  containing  the  residue  insoluble  in  ether  are  then 
removed  from  the  extraction  apparatus,  the  excess  of  ether  in  the 
residue  is  removed  by  suction,  and  the  crucibles  with  their  contents 
are  placed  at  once  in  a  drying  oven. 

DRYING  OF  INSOLUBLE  RESIDUE. 

The  method  of  drying  this  residue  depends  upon  whether  or  not 
the  qualitative  analysis  has  shown  the  presence  of  ammonium  salts 
or  other  substances  that  may  be  volatilized  or  decomposed  on  heating. 
If  the  explosive  does  not  contain  ammonium  salts,  it  is  customary 
to  dry  the  residue  at  a  temperature  of  100°  C.  for  5  hours,  a  pro- 
cedure that  has  been  found  to  insure  constant  weight.  A  longer 
period  of  drying,  even  overnight,  will  not  cause  any  appreciable  addi- 
tional loss  in  weight,  and  is  often  found  convenient. 

If  ammonium  salts  are  present,  the  residue  is  dried  at  a  tempera- 
ture of  70°  C.,  as  it  has  been  shown 6  that,  especially  in  the  presence 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
61,  Bureau  of  Mines,  1913,  pp.  30-32. 

6  Snelling,  W.  O.,  and  Storm,  C.  G.,  op.  cit.,  pp.  59-60. 


34  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

of  zinc  oxide,  the  antacid  generally  employed  in  ammonium  nitrate 
explosives,  an  appreciable  loss  of  the  ammonium  salts  results  from 
drying  at  100°  C.  At  70°  the  loss  was  found  to  be  practically  negli- 
gible, even  on  drying  for  a  period  of  24  hours. 

Organic  nitrates,  such  as  nitrostarch  or  nitrocellulose,  may,  if  pres- 
ent, also  undergo  some  decomposition  if  the  residue  is  dried  as  long 
as  5  hours  at  100°  C.  When  the  qualitative  examination  has  indicated 
the  presence  of  either  of  these  substances,  it  is  advisable,  therefore, 
to  dry  the  residue  at  70°  instead  of  100°. 

After  the  drying  is  completed  the  crucibles  are  transferred  from 
the  drying  oven  to  sulphuric-acid  desiccators,  allowed  to  cool  for  15 
to  20  minutes,  and  immediately  weighed. 

The  loss  of  weight  represents  the  ether-soluble  material  plus  the 
moisture  originally  contained  in  the  sample  before  extraction.  If 
salts  containing  water  of  crystallization  are  a  constituent  of  the  ex- 
plosive, this  loss  of  weight  also  includes  part  of  the  combined  water  in 
addition  to  the  free  moisture.  For  example,  crystallized  magnesium 
sulphate,  MgSO4.7H2O,  if  heated  sufficiently  long  at  100°  C.,  loses  5 
molecules  of  its  water  of  crystallization.  In  the  absence  of  such 
hydrated  salts  the  total  loss  obtained  by  extraction  with  ether,  minus 
the  moisture  determined  by  desiccation,  is  taken  as  the  amount  of 
ether-soluble  material,  but  when  hydrated  salts  are  present  the  direct 
weight  of  residue  left  on  evaporation  of  the  ether  solution  should  be 
taken  as  representing  the  total  ether-soluble  material. 

MODIFIED  TUBE  FOB  WILEY  EXTRACTION  APPARATUS. 

A  modified  glass  tube  for  use  with  the  Wiley  extraction  apparatus 
is  shown  in  figure  4.  This  form  of  tube  was  suggested  to  the  writer 
by  F.  B.  Stieg,  chemist  of  the  Aetna  Powder  Co.,  Aetna,  Ind.,  who 
had  devised  it  for  his  own  use.  These  tubes  are  in  use  in  the  labora- 
tory of  the  Bureau  of  Mines,  and  are  found  especially  suitable  for 
ether  extractions  of  explosives  containing  solids,  such  as  trinitro- 
toluene and  sulphur,  which  are  soluble  in  ether  and  which  crystallize 
out  in  the  extraction  tube  during  the  process  of  extraction. 

When  the  usual  style  of  extraction  tube a  is  used  it  is  necessary  to 
transfer  the  ether  extract  to  small,  weighed  beakers  before  evaporat- 
ing the  ether.  The  presence  of  crystals  in  the  extract  renders  this 
transference  more  or  less  troublesome  and  necessitates  the  use  of  an 
unusual  amount  of  ether  for  completely  removing  all  of  the  crystal- 
lized material  from  the  tube. 

The  modified  tube  shown  in  figure  4  is  approximately  the  same  size 
as  the  usual  extraction  tube,  but  is  made  in  two  parts,  the  bottom  part 

a  For  description  and  view,  see  Snelling,  W.  OM  and  Storm,  C.  G.,  The  analysis  of  black 
powder  and  dynamite  :  Bull.  51,  Bureau  of  Mines,  1913,  pp.  31,  32. 


QUANTITATIVE   ANALYSIS. 


35 


!• 2tf ( 

I  ^-Ground  face      I 


being  2J  inches  deep  and  1  j  inches  inside  diameter,  and  made  of  glass 
of  such  thickness  that  its  weight  is  approximately  30  grams.  The  two 
parts  are  connected  by  means  of  a  wide 
ground  joint  between  the  outer  surface, 
of  the  bottom  part  and  the  inner  sur- 
face of  the  upper  part.  This  ground 
joint  becomes  wet  with  ether  during 
the  extraction  and  is  thus  rendered 
perfectly  tight. 

In  using  this  extraction  tube  the  bot- 
tom part  is  carefully  dried  and  weighed 
before  beginning  the  extraction.  Af- 
ter the  extraction  is  completed  the  bot- 
tom part,  containing  the  ether  extract, 
is  removed,  placed  under  the  bell- jar 
evaporator,  and  the  ether  evaporated 
in  a  current  of  dry  air.  The  ether- 
soluble  extracted  material  is  then  in 
condition  to  be  weighed,  unless  the 
explosive  contained  a  considerable 
amount  of  moisture,  in  which  case 
desiccation  is  necessary  in  order  to 
obtain  approximately  constant  weight. 

Naturally  this  style  of  tube  can  not 
be  suspended  from  a  ring  support,  but 
must  be  allowed  to  rest  on  the  top  of 
the  heating  bath  in  order  to  prevent 
the  bottom  part  of  the  tube  from  be- 
coming detached. 


EVAPORATION  IN  THE 
EVAPORATOR. 


BELL-JAR 


T 


The  apparatus  used  in  the  bureau's 
laboratory  for  evaporating  the  ether 
extract  is  shown  in  figure  5.  It  is 
known  as  the  bell- jar  evaporator  and 
was  devised  by  A.  L.  Hyde,  assistant 
explosives  chemist.  The  beaker,  «, 
containing  the  ether  solution  is  placed  , 

0  FIGURE  4. — Modified  glass   tube   for 

on  a  ground-glass  plate,  5,  and  covered        use  with   Wiley   extraction   appa- 

by   a   glass   bell   jar,   <?,   6   inches   in      ratus- 

diameter  and  8  inches  high,  with  tubulures  at  the  top  and  on  the  side, 
each  opening  being  fitted  with  a  perforated  stopper  and  delivery 
tube.  A  current  of  compressed  air,  dried  by  passing  through  con- 


36 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


centrated  sulphuric  acid  in  a  drying  cylinder,  d,  is  passed  through 
the  delivery  tube  in  the  top  of  the  bell  jar,  the  lower  end  of  the  tube 
being  adjusted  about  one-half  inch  above  the  surface  of  the  ether 
solution  in  the  beaker.  A  drying  cylinder,  e,  filled  with  granular 
soda  lime  is  connected  between  the  sulphuric  acid  cylinder  and  the 
bell  jar  in  order  to  prevent  traces  of  acid  from  being  mechanically 
carried  over.  The  upper  and  lower  ends  of  the  soda-lime  tower  are 
charged  with  cotton,  /,  which  serves  as  a  filter  for  the  air.  The  air 
current  is  so  regulated  that  a  marked  "  dimple  "  is  made  in  the  sur- 
face of  the  solution,  care  being  taken  to  avoid  loss  by  spattering 
through  using  too  high  an  air  pressure.  The  ether  vapors  pass  out 
through  the  tube  in  the  side  tubulure  and  may  be  conducted  out  of 
the  laboratory. 


FIGUEE  5. — Apparatus  for  evaporating  ether  extract 

The  advantage  in  the  use  of  this  method  of  evaporating  ether 
solutions  of  nitroglycerin  lies  in  the  fact  that  the  low  temperature 
produced  by  the  rapid  evaporation  of  the  ether  minimizes  the  vola- 
tilization of  the  nitroglycerin  and,  the  air  current  being  dry,  there  is 
no  deposition  of  moisture  from  the  air,  so  that  it  is  only  necessary  to 
desiccate  the  residue,  after  evaporation  of  the  ether,  for  a  sufficient 
time  to  remove  the  original  moisture. 

A  weighed  quantity  of  nitroglycerin  may  be  dissolved  in  50  c.  c. 
of  ether  and  the  ether  evaporated  completely  in  a  few  hours  with  a 
loss  of  less  than  1  milligram  of  nitroglycerin,  as  shown  by  the 
nitrometer  determinations  given  on  page  38. 

ANALYSIS  OF  ETHER  EXTRACT. 

The  duplicate  portions  of  the  ether-soluble  material,  after  all  the 
ether  has  been  removed,  as  determined  by  check  weighings,  are  then 
ready  for  examination.  If  qualitative  tests  have  indicated  the  pres- 


QUANTITATIVE   ANALYSIS.  37 

ence  of  nitroglycerin,  one  of  the  duplicate  samples  is  used  for  de- 
termining nitroglycerin  by  means  of  the  nitrometer,  as  described  in 
Bulletin  51,°  and  the  other  sample  is  used  for  the  determination  of 
any  ingredients  other  than  nitroglycerin.  Frequently  it  is  necessary 
to  extract  additional  samples  of  the  original  explosive  with  ether, 
in  order  to  obtain  a  sufficient  number  of  samples  of  the  ether  extract 
for  the  necessary  determinations. 

EFFECT    OF    VOLATILITY    OF    NITRO    COMPOUNDS    AND    NITROGLYCERIN    ON 
THE  RESULTS  OF  THE  ANALYSIS. 

The  accuracy  of  the  analysis  of  the  ether-soluble  part  of  most  per- 
missible explosives  is  more  or  less  affected  by  certain  properties  of 
substances  usually  present.  For  example,  nitroglycerin  and  some  of 
the  nitrosubstitution  products  are  appreciably  volatile  under  certain 
conditions,  and  in  the  determination  of  nitroglycerin  by  means  of 
the  nitrometer  some  of  the  other  constituents  may  take  up  appre- 
ciable amounts  of  the  nitric  acid  liberated  from  the  nitroglycerin, 
thereby  introducing  an  error  in  the  nitroglycerin  determination. 

These  chief  sources  of  error  have  been  investigated  and  the  results 
of  experiments  made  are  here  described. 

LOSS   OF  NITBOGLYCERIN  DURING  EVAPORATION   OF  THE  ETHER   SOLUTION. 

The  subject  of  loss  of  nitroglycerin  by  volatilization  has  been  con- 
sidered in  Bulletin  51,&  where  experiments  are  described  showing 
that  spontaneous  evaporation  of  the  ether  at  room  temperature 
results  in  very  slight  loss  of  nitroglycerin.  The  main  objection  to 
this  method  of  evaporation  is  the  fact  that  an  appreciable  amount  of 
moisture  from  the  air  is  deposited  with  the  extract,  necessitating 
desiccation  for  considerable  periods.  The  use  of  the  bell- jar  evapo- 
rator described  in  a  preceding  paragraph  prevents  the  deposition 
of  moisture.  A  large  number  of  tests  have  been  carried  out  to  deter- 
mine the  loss  of  nitroglycerin  in  evaporating  ether  extracts  with  the 
bell  jar. 

Weighed  samples  of  nitroglycerin  were  each  dissolved  in  50  c.  c. 
of  ether  in  100-c.  c.  beakers.  The  ether  was  volatized  by  subjecting 
the  solution  to  a  current  of  dry  air  for  a  definite  length  of  time  in 
the  bell- jar  evaporator,  then  the  residue  of  nitroglycerin,  containing 
possible  traces  of  moisture  and  ether,  was  weighed,  and  the  actual 
proportion  of  nitroglycerin  determined  by  means  of  the  nitrometer, 

a  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  35-38. 

6  Snelling,  W.  O.,  and  Storm,  C.  G.,  op.  cit.,  pp.  39—11. 


ANALYSIS  OF   PERMISSIBLE  EXPLOSIVES. 


the  use  of  which  is  fully  described  in  Bulletin  51.°  A  number  of 
such  determinations  are  shown  in  the  following  table,  in  which 
column  1  gives  the  quantity  of  nitroglycerin  (99.6  per  cent  pure) 
taken,  column  2  the  time  of  treatment  of  the  ether  solution  with 
the  air  current,  columns  3  and  4  the  variation  of  the  final  weight 
from  the  original  weight  of  nitroglycerin,  column  5  the  quantity  of 
nitroglycerin  (calculated  to  original  purity,  99.6  per  cent)  in  the 
evaporated  residue  as  determined  by  means  of  the  nitrometer,  and 
column  6  the  actual  loss  of  nitroglycerin,  or  difference  between  the 
results  in  column  1  and  column  5. 

Loss  of  nitroglycerin  by  evaporation  of  ether  solutions  ly  means  of  dry-air  cur- 
rent in  bell-jar  evaporator. 


Test  No. 

Quantity 
of  nitro- 
glycerin 
taken  for 
test. 

1 

Time  of 
evapora- 
tion. 

2 

Change  in  weight. 

Quantity 
of  nitro- 
glycerin in 
residue  as 
determined 
by  nitrom- 
eter. 

5 

Loss  of 
nitroglyc- 
erin. 

6 

Gain. 
3 

Loss. 
4 

1... 

Gram. 
0.  7152 
.7025 
.7067 
.7091 
.7041 
.7271 
.7014 
.7038 
.7127 
.7260 
.7019 

Hours. 
2 
2 
3 
3 
3 
4 
4 
4 
4 
18 
18 

Gram. 
0.0033 
.0001 

Gram. 

Gram. 
0.7148 
.7016 
.7067 
.7077 
.7023 
.7263 
.7012 
.7028 
.7105 
.7236 
.6974 

Gram. 
0.0004 
.0009 
.0000 
.0014 
.0018 
.0008 
.0002 
.0010 
.0022 
.0024 
.0045 

2 

3  

0.0003 

4 

.0004 

5  

.0002 

6  . 

.0003 
.0005 

7 

8  

.0005 
.0006 
.0065 
.0064 

9 

10 

11. 

The  results  indicate  that  by  evaporating  the  ether  extracts  in  a 
dry  air  current,  using  the  bell- jar  evaporator,  it  is  possible  to  remove 
practically  all  of  the  ether  in*  a  few  hours  without  serious  loss  of 
nitroglycerin,  and  without  absorption  of  moisture,  obviating  the 
necessity  of  desiccating  the  evaporated  residue  before  weighing. 

In  most  of  the  results  cited  the  weight  of  the  evaporated  residue 
is  greater  than  that  of  the  original  sample,  owing  to  some  deposition 
of  moisture  or  to  ether  residue;  in  other  tests,  for  example,  Nos.  10 
and  11,  the  weight  of  evaporated  residue  is  less  than*  the  weight  of 
99.6  per  cent  nitroglycerin  calculated  from  the  nitrometer  determina- 
tion, because  some  of  the  moisture  present  in  the  original  nitrogly- 
cerin had  been  evaporated  by  the  long-continued  treatment  and  the 
purity  of  the  nitroglycerin  actually  increased  thereby.  The  ether 
used  in  these  experiments  was  good  quality  U.  S.  P.  ether  and  con- 
tained a  negligible  proportion  of  nonvolatile  residue. 

«  Snelling,  W.  O.,  and  Storm,  C.  G.,  op.  cit,  p.  38 


QUANTITATIVE  ANALYSIS. 


EFFECT   OF   RATE   OF    AIR   CURRENT    ON    EVAPORATION   OF    NITROGLYCERIN. 

The  rate  of  evaporation  and  the  loss  of  nitroglycerin  for  a  given 
period  of  treatment  with  the  dry  air  current  naturally  depend  on 
the  rate  of  the  air  current.  The  table  following  shows  the  results  of 
two  tests  in  which  the  samples  of  nitroglycerin  were  each  dissolved 
in  50  c.  c.  of  ether  and  the  ether  evaporated  as  above  described.  A 
more  rapid  air  current  was  used  to  evaporate  sample  2,  so  that  in  a 
given  period  of  time  the  volume  of  air  passed  over  sample  2  was 
greater  than  that  passed  over  sample  1,  as  indicated  by  the  passage  of 
air  through  the  sulphuric  acid  in  the  drying  cylinders. 

Variation  in  rate  of  loss  of  nitroglycerin  ~by  evaporation  of  ether  solutions  in 

dry  air  current. 


Time  of  evaporation. 

Sample  1. 

Sample  2. 

Weight  of 
nitrogly- 
cerin. 

Change  in  weight. 

Weight  of 
nitrogly- 
cerin. 

Loss  in 
weight. 

Gain. 

Loss. 

Hours. 
0                                        

Grams. 
1.  2278 

Gram. 

Gram. 

Gram. 
0.7019 
.7027 

Gram. 

3 

1.2547 
1.  2390 
1.  2345 
1.2325 
1.2299 
.2270 

0.  0269 
.0112 
.0067 
.0047 
.0021 

a  0.0008 

4                                 

5 

.7018 
.7016 
.7007 

.0001 
.0003 
.0012 

6  .                     

7                                                    

8  

0.0008 

9                        

.2269 

.0009 
.0007 
.0001 
.0013 
.0016 
.0018 
.0020 
.0020 

.7002 
.6999 
.6986 
.6976 
.6973 
.6968 
.6966 

.0017 
.0020 
.0033 
.0043 
.0046 
.0051 
.0053 

10 

2271 

11     

.2277 

12 

2265 

13... 

.2262 
.2260 

14 

15 

2258 

16  

.2258 

17     . 

1.2257 

.0021 

.6961 
.6955 

.0058 
.0064 

18  

a,  Gain. 

The  results  show  that  a  rapid  air  current  removes  the  ether  in  a 
shorter  time  (3  to  5  hours),  but  that  for  long  periods  of  treatment 
more  nitroglycerin  is  lost  than  with  a  slower  air  current. 

It  is  important  that  the  air  current  should  not  be  strong  enough  to 
cause  mechanical  loss  of  the  nkroglycerin  by  spattering. 

LOSS    OF    NITROTOLUENES    DURING   EVAPORATION    OF   THE   ETHER    SOLUTION. 

Experiments  were  also  made  to  determine  to  what  extent  the  vari- 
ous nitrotoluenes  are  lost  by  volatilization  during  evaporation  of  the 
ether  from  ether  solutions  containing  them.  In  the  tests  described 
below  approximately  1  gram  of  each  sample  was  dissolved  in  50 
c.  c.  of  U.  S.  P.  ether  in  a  100  c.  c.  beaker  and  the  ether  evaporated 
in  the  bell- jar  evaporator,  weighings  being  made  at  intervals  in  order 
to  determine  any  loss  of  nitro  compound. 


40 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


Results  of  experiments  to  determine  loss  of  nitrotoluenes  by  evaporation  of  ether 
solutions  with  a  dry  air  current  in  bell-jar  evaporator. 


Time  of  evaporation. 

Mononitrotoluene 
(G)  (ortho). 

Mononitrotoluene 
(H)  (para). 

Dinitrotoluene  a  (F)  (crystals). 

Weight  of 
sample. 

Loss  in 
weight. 

Weight  of 
sample. 

Loss  in 
weight. 

Weight  of 
sample. 

Change  in  weight. 

Gain. 

Loss. 

Hours. 
0                 

Grams. 
1.0025 

Gram. 

Grams. 
1.0072 

Gram. 

Grams. 
1.0000 

Gram. 

Gram. 

2 

.9905 
.9640 
.9375 
.9103 
.8815 
.8468 
.8397 
.8275 
.8175 
.8047 
.7915 

0.0167 
.0432 
.0697 
.0969 
.  1257 
.1604 
.1675 
.1797 
.1897 
.2025 
.2157 

1.0285 
1.0020 
1.0009 
1.0003 
.9995 
.9987 
.9980 
.9976 
.9976 
.9972 
.9967 

0.  0285 
.0020 
.0009 
.0003 

3  .    .                          

.9450 
.9146 

.8850 
.8575 

0.  0575 
.0879 
.1175 
.1450 

4 

5 

6 

0.0005 
.0013 
.0020 
.0024 
.0024 
.0028 
.0033 

7 

g 

.8000 
.7770 
.7450 
.7184 
.6914 

.2025 
.2255 
.2575 
.2841 
.3111 

g 

10 

11  

12 

Time  of  evaporation. 

Trinitrotoluene  & 
(E)  (crystals). 

Dinitrotoluene  (D)  (liquid). 

Dinitrotoluene  (C) 
(liquid). 

Weight  of 
sample. 

Gain  in 
weight. 

Weight  of 
sample. 

Change  in  weight. 

Weight  of 
sample. 

Loss  in 
weight. 

Gain. 

Loss. 

Hours. 

o 

Grams. 
1.0000 

Gram. 

Grams. 
1.0012 

Gram. 

Gram. 

Grams. 
1.0110 

Gram. 

2 

3 

1.0000 
1.0000 
1.0000 
1.0000 

0.0000 
.0000 
.0000 
.0000 

.0354 
.0183 
.0102 
.0062 
.0023 
.9961 
.9944 

0.  0342 
.0171 
.0090 
.0050 
.0011 

1.  0505 
1.  0240 
1.  0102 
1.  0030 
.9959 
.9875 
.9852 
.9825 
.9795 
.9780 

c  0.  0395 
c  .  0130 
.0008 
.0080 
.0151 
.0235 
.0258 
.0285 
.0315 
.0330 

4 

5 

6 

7 

8. 

.9995 

d.0005 

0.0051 

.0068 
.0079 
.0088 
.0097 

g 

10 

.9933 

11 

.9924 

12 

.9915 

Time  of  evaporation. 

TriQitrotcluene  (B)  (liquid). 

Trinitrotoluene  (A)  (liquid). 

Weight  of 
sample. 

Change  in  weight. 

Weight  of 
sample. 

Change  in  weight. 

Gain. 

Loss. 

Gain. 

Loss. 

Hours. 
0 

Grams. 
1.  0137 

Gram. 

Gram. 

Grams. 
1.0225 

Gram. 

Gram. 

2 

3.               .   .                                         .   .   .. 

1.0450 
1.0303 
1.0250 
1.  0215 
1.  0175 
1.  0130 

0.  0313 
.0166 
.0113 
.0078 
.0038 

.0650 
.0450 
.0355 
.0305 
.0266 
.0225 
.0217 
.0214 
.0210 
1.0200 

0.0425 
.0225 
.0130 
.0080 
.0041 
.0000 

4 

5. 

6 

7 

s 

0.0007 
.0029 
.0042 
.0063 
.0076 

9      

1.  0108 

0.0008 
.0011 
.0015 
.0025 

10 

1  0095 

11  

1.0074 

12 

1  0061 

a  Melting  point  66°  to  68°  C. 


b  Melting  point  81°  to  82°  C. 


Gain. 


d  Loss. 


The  results  are  what  might  be  expected  from  the  results  of  deter- 
mination of  volatility  in  desiccators,  described  in  pages  24  to  29. 


QUANTITATIVE  ANALYSTS.  41 

The   loss   of   crystalline   trinitrotoluene    during   evaporation   by 
[    means  of  the  air  current  was  negligible.     The  same  was  true  for 
I   crystalline  dinitrotoluene  for  periods  amply  sufficient  to  remove  all 
ether,  although  the  gradual  loss  beyond  this  point  indicates  that 
dinitrotoluene  is  slightly  volatile.     Both  orthomononitrotoluene  and 
paramononitrotoluene  volatilized  appreciably,  even  before  the  evap- 
oration of  the  ether  was  complete.     The  evaporation*  of  the  ether 
from   the  "liquid*  dinitrotoluenes "   and   "liquid  trinitrotoluenes" 
i    apparently  proceeded  more  slowly  than  from  the  crystalline  com- 
pounds, 5  to  8  hours'  treatment  being  necessary  before  the  liquid 
I   samples  attained  approximately  their  original  weight. 

On  further  treatment  with  the  air  current  the  "  liquid  trinitroto- 
luenes "  underwent  a  slight  loss  of  weight  and  the  "  liquid  dinitroto- 
luenes" a  somewhat  greater  loss.  In  general,  it  is  noted  that  the 
loss  of  weight  is  greater  as  the  percentage  of  mononitrotoluene  is 
greater. 

CONCLUSIONS    REGARDING    LOSS    BY    EVAPORATION    OF    THE    ETHER    EXTRACT. 

The  experiments  indicate  that  by  the  use  of  the  bell- jar  evapo- 
rator, with  a  fairly  rapid  current  of  dry  air,  ether  solutions  may  be 
evaporated  in  about  5  to  6  hours  without  an-  appreciable  loss  of  either 
nitroglycerin  or  nitrotoluenes,  provided  that  no  great  proportion  of 
mononitrotoluene  is  present.  Seven  to  eight  hours  may  be  necessary 
for  complete  removal  of  the  ether  from  "liquid  trinitrotoluene,"  and 
even  an  8-hour  treatment  will  not  cause  any  appreciable  loss  of 
nitroglycerin. 

EFFECT  OF  VARIOUS  SUBSTANCES  ON  THE  DETERMINATION  OF  NITRO- 
GLYCERIN  BY  MEANS  OF  THE  NITROMETER. 

It  has  been  shown  a  that  mononitrotoluene,  which  is  usually  a  con- 
stituent, in  greater  or  less  proportion,  of  most  of  the  commercial 
"liquid*  nitrotoluenes"  used  in  blasting  explosives,  interferes  with 
the  direct  determination  of  nitroglycerin  by  means  of  the  nitrometer. 
Other  mononitro  compounds  ajffect  the.  determination  in  the  same 
manner,  by  combining  with  part  of  the  nitric  acid  resulting  from 
the  breaking  up  of  the  nitroglycerin.  Certain  substances  other  than 
nitrosubstitution  compounds,  which  may  be  found  in  the  ether  ex- 
tracts of  explosives,  have  the  same  effect.  A  series  of  experiments 
were  made  in  order  to  determine  the  extent  to  which  the  determina- 
tion of  nitroglycerin  in  the  nitrometer  is  affected  by  the  presence  of 
such  substances  as  may  be  contained,  with  the  nitroglycerin  in  the 
ether  extract. 

0  Storm,  C.  G.,  Effect  of  nitrotoluenes  on  the  determination  of  nitroglycerin  by  means 
oi?  the  nitrometer :  Original  Communications,  8th  Int.  Cong.  App.  Chem.,  vol.  4,  1912, 
p.  117. 


42 


ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 


TESTS  OF  ETHEB-SOLUBLE  SUBSTANCES. 

The  substances  used  in  these  tests  included  the  more  common  nitro- 
substitution  compounds,  rosin  (colophony),  vaseline,  paraffin,  and 
various  mineral  and  vegetable  oils.  A  weighed  quantity  of  the 
material  to  be  tested  was  placed  in  a  small  beaker,  a  weighed  quan- 
tity of  either  nitroglycerin  or  potassium  nitrate  of  known  nitrogen 
content  (18.46  and  13.84  per  cent,  respectively)  added,  and  the  whole 
treated  with  about  10  c.  c.  of  strong  sulphuric  acid,  approximately 
96  per  cent  pure.  The  mixture  was  well  stirred  with  a  small  glass 
rod  and  transferred  to  the  generating  bulb  of  the  nitrometer,  fresh 
sulphuric  acid  being  used  to  completely  remove  any  undissolved 
material  left  in  the  beaker.  In  most  of  the  tests  20  to  30  c.  c.  of  sul- 
phuric acid  was  sufficient.  After  shaking  the  mixture  in  the  genera- 
tor until  the  evolution  of  nitric  oxide  (NO)  was  complete,  the  gas 
was  transferred  to  the  reading  tube  and  the  volume  read.  This 
reading  is  expressed  in  terms  of  weight  of  nitrogen  found  (grams) 
in  column  4  of  the  following  taJble  of  results.  The  figures  given  in 
column  5  for  the  weight  of  nitrogen*  lost  per  gram  of  ingredient 
(column  3)  are  obtained  by  deducting  the  weight  of  nitrogen  found 
(column  4)  from  the  weight  of  nitrogen  present  (weight  of  KNO3 

times      '     ?  or  weight  of  nitroglycerin  times    ^  ),  and  dividing 


the  remainder  by  the  weight  of  substance  as  given  in  column  3. 
Column  5  also  shows  the  equivalent  of  the  nitrogen  loss  in  terms  of 
nitroglycerin  ;  or,  in  other  words,  the  loss  of  nitroglycerin  which 
would  result  from  the  presence  of  1  gram  of  the  substance  indicated 
in  column  3. 

Results  of  determinations  of  nitrogen  in  the  nitrometer  in  the  presence  of  vari- 
ous ether-soluble  substances. 

VASELINE. 


Weights  of  ingredients  of  mixture. 

Results  of  determination. 

KN03. 

Nitroglyc- 
erin. 

Substance 
tested. 

Weight  of 
N  found. 

Weight  of 
N  lost  per 
gram  of 
substance 
tested. 

Average 
loss  of  N 
per  gram  of 
substance 
tested. 

Equivalent 
loss  of  nitro- 
glycerin 
per  gram  of 
substance 
tested. 

1 

2 

3 

4 

5 

6 

7 

Gram. 
1.0000 
1.0000 
1.0000 

Gram. 

Gram. 
0.4006 
.2052 
.1046 
.2010 

Gram. 
0.1302 
.1335 
.  1364 
.1281 

Gram. 
0.0205 
.0239 
.0191 
.0239 

Gram. 
0.0218 

Gram. 
0.1180 

0.7192 

QUANTITATIVE   ANALYSIS. 


43 


Results  of  determinations  of  nitrogen  in  the  nitrometer  in  the  presence  of  vari- 
ous ether-soluble  substances — Continued. 

PARAFFIN. 


Weights  of  ingredients  of  mixture. 

Results  of  determination. 

KN03. 

Nitroglyc- 
erin. 

Substance 
tested. 

Weight  of 
N  found. 

Weight  of 
N  lost  per 
gram  of 
substance 
tested. 

Average 
loss  of  N 
per  gram  of 
substance 
tested. 

Equivalent 
loss  of  nitro- 
glycerin 
per  gram  of 
substance 
tested. 

1 

2 

3 

4 

5 

6 

7 

Gram. 
1.0000 

Gram. 

Gram. 
0.  1670 
.1012 

Gram. 
0.1358 
.1391 

Gram. 
0.0155 
.0158 

Gram. 
}     0.0157 

Gram. 
0.0849 

0.7624 

CASTOR  OIL. 


1.2000 

0.1688 
.1557 

0.1564 
.1475 

0.0575 
.0591 

}      0.0583 

0.3151 

0.8491 

COTTONSEED  OIL. 

1.0000 
1.0000 

0.4229 
.2311 

0.1025 
.1187 

0.0849 
.0852 

}      0.0851 

0.4589 

ENGINE  OIL. 

1.0000 
1.0000 

0.1050 
.3192 
.1592 

0.1334 
.1229 
.1294 

0.0476 
.0485 
.0484 

i      0.0482 

0.2605 

0.7428 

CORN  OIL. 

1.0000 

0.1054 
.2044 

0.  1316 
.1430 

0.0645 
.0600 

}      0.0623 

0.3368 

0.8416 

ROSIN  (COLOPHONY). 

0.7552 
.7394 
.7590 

0.1006 
.1008 
.2017 

0.  1316 
.1289 
.1248 

0.0775 
.0744 
.0758 

\     0.0759 

0.4103 

MONONITRONAPHTHALENE. 

.0000 
.0000 
.0000 
.0000 
.0000 

0.1000 
.2012 
.3000 
.1006 
.1627 
.2520 

0.  1219 
.1061 
.0894 
.1219 
.1140 
.1045 

0.1650 
.1605 
.1633 
.1640 
.1598 
.1600 

0.  1621 

0.8762 

0.7846 

MONONITROBENZENE. 

1.3190 
1.3053 

1.0017 
.9981 

0.1276 
.1259 

0.  1157 
.1152 

}      0.  1155 

0.6243 

DINITROBENZENE. 

1.0000 

0.  1966 
.9993 

0.  1384 
.1311 

0.0000 
.0007 

0.0000 
.0007 

0.  7139 

44  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

DISCUSSION    OF   RESULTS   OF   TESTS. 

The  above  results  show  that  such  materials  as  rosin,  vaseline, 
paraffin,  and  mineral  and  vegetable  oils  are  all  capable  of  being 
nitrated,  and  hence  take  up  part  of  the  nitric  acid  liberated  from  the 
nitroglycerin  by  the  reaction  in  the  nitrometer.  Furthermore,  the 
proportion  of  nitrogen  thus  combined  by  such  materials  is  practi- 
cally a  constant  quantity  for  each  gram  of  the  material,  regardless 
of  the  quantity  present. 

All  mononitro  compounds  are  probably  capable  of  becoming  fur- 
ther nitrated  under  the  conditions  existing  in  the  nitrometer,  and  the 
tests  made  indicate  that  in  each  instance  the  mononitro  compound  is 
nitrated  to  a  definite  degree,  taking  up  either  one  or  two  more  nitro 
groups.  The  previous  work  of  the  writer,0  referred  to  in  a  preceding 
paragraph,  showed  that  the  mononitrotoluenes  are  quantitatively 
converted  to  dinitrotoluenes  but  that  dinitrotoluenes  and  trinitro- 
toluenes are  not  acted  on  in  the  nitrometer.  The  results  in  the  table 
show  analogous  action  of  mononitrobenzene  and  dinitrobenzene ; 
1  gram  of  mononitrobenzene  absorbed  0.1152  gram  nitrogen,  whereas 
for  conversion  to  dinitrobenzene  it  should  absorb  0.1138  gram. 
Dinitrobenzene  was  practically  without  effect  on  the  determination. 
Mononitronaphthalene,  however,  was  converted  by  the  reaction  in 
the  nitrometer  to  trinitronaphthalene,  1  gram  of  the  mono  compound 
taking  up  0.1621  gram  of  nitrogen,  whereas  the  quantity  theoretically 
required  for  the  conversion  to  trinitronaphthalene  is  0.1597  gram. 

This  conclusion  was  confirmed  by  the  following  experiment:  2 
grams  of  mononitronaphthalene  was  added  to  2.4  grams  potassium 
nitrate  and  the  mixture  treated  in  a  beaker  with  about  25  c.  c.  of 
96  per  cent  sulphuric  acid,  stirred,  and  let  stand  for  2  hours  until 
cooled  to  room  temperature.  The  mixture  was  then  poured  into  500 
c.  c.  water,  the  resulting  precipitate  filtered  off,  washed,  and  dried 
to  constant  weight  in  a  vacuum  desiccator.  The  product  weighed 
2.94  grams,  whereas  if  the  mono  compound  had  been  completely  con- 
verted to  trinitronaphthalene  the  weight  should  have  been  3.04  grams. 
The  original  mononitronaphthalene,  which  theoretically  contained 
8.09  per  cent  nitrogen,  was  found  to  contain  8.16  per  cent  nitrogen, 
and  the  product  obtained  by  the  above  reaction  contained  15.67 
per  cent  nitrogen,  whereas  trinitronaphthalene  theoretically  con- 
tains 15.97  per  cent  of  nitrogen. 

The  interference  of  ether-soluble  substances  with  the  determina- 
tion of  the  nitroglycerin  may  be  avoided  if  any  substances  in  the 
ether  extract  other  than  nitroglycerin  are  determined  by  a  direct 
method  and  the  nitroglycerin  determined  by  difference.  The  direct 

«  Storm,  C.  G.,  Effect  of  nitrotoluenes  on  the  determination  of  nitroglycerin  by  means 
of  the  nitrometer :  Original  Communications ;  8th  Int.  Cong.  App.  Chem.,  vol.  4,  1912, 
p.  117. 


QUANTITATIVE   ANALYSIS. 


45 


determination  of  these  ether-soluble  materials  is  discussed  in  pages 
46  and  47. 

TESTS  TO  ASCERTAIN   SOLUBILITY  OF  ETHER-SOLUBLE  SUBSTANCES  IN  NITROGLYCERIN. 

A  series  of  tests  was  made  to  ascertain  the  extent  to  which  the 
solubility  of  these  ether-soluble  substances  in  the  nitroglycerin  would 
affect  the  determination  of  the  purity  of  the  nitroglycerin  separated 
from  such  substances  by  filtration.  About  0.5  gram  of  the  substance 
taken  for  test  was  added  to  2  c.  c.  of  nitroglycerin  of  known  nitrogen 
content  (18.42  per  cent),  the  whole  dissolved  in  50  c.  c.  of  ether,  the 
ether  evaporated  by  the  method  described  for  treating  the  ether  ex- 
tract of  an  explosive  (pp.  35  and  36) ,  the  evaporated  material  filtered 
through  a  paper  filter,  and  the  clear  filtrate  tested  in  the  nitrometer. 
From  the  result  of  the  nitrogen  determination  it  is  readily  ascer- 
tained whether  an  appreciable  quantity  of  the  substance  has  been  dis- 
solved by  the  nitroglycerin.  For  example,  a  determination  giving 
a  nitrogen  content  of  18.32  per  cent  indicates  that  1  per  cent  of  the 
substance  is  dissolved  in  the  filtered  nitroglycerin;  18.13  per  cent  N 
indicates  that  2  per  cent  of  the  substance  has  been  dissolved,  and  so 
on,  provided  that  any  nitrogen  taken  up  by  the  dissolved  material 
is  disregarded. 

The  table  following  shows  the  results  of  the  tests  made : 

Results  of  tests  to  determine  nitrogen  content  in  nitroglycerin  filtered  from 
various  ether-soluble  substances. 


Substance  with  which  nitroglycerin 
was  mixed. 

Nitrogen 
content  of 
filtered 
nitro- 
glycerin. 

Substance  with  which  riitroglycerin 
was  mixed. 

Nitrogen 
content  of 
filtered 
nitro- 
glycerin. 

Per  cent. 
f          18  42 

Engine  oil 

Per  cent. 
18  16 

Vaseline  refined 

I            to 

Corn  oil  

18  35 

18.37 

Mononitronaphthalene 

13  44 

Vaseline,  crude.              

18.39 

Mononitrotoluene  (para)  

14.94 

f           18.  37 

Dinitrotoluene  (crystals)  & 

15  60 

Paraffin  

\              to 

Trinitrotoluene  (crystals)  &  

15.43 

Sulphur 

18.42 
18.43 

Resins  extracted  from  wood  pulp: 
Sample  1. 

17  96 

f           18.  07 

Sample  2  

17.78 

Rosin  (colophony) 

\              to 

Sample  3. 

17.77 

18.05 

Oil  extracted  from  corn  meal  

18.42 

Castor  oil 

18.43 

Oil  extracted  from  wheat  middlings 

18.43 

Cottonseed  oil  

18.44 

a  Melting  point,  66°  to  68°  C.  *>  Melting  point,  81°  to  82°  C. 

The  above  results  show  that  vaseline,  paraffin,  sulphur,  cottonseed 
oil,  castor  oil,  corn  oil,  and  wheat  oil  are  practically  insoluble  in 
nitroglycerin,  and  that  the  nitroglycerin  mixed  with  them  may  be 
obtained  in  sufficient  purity,  for  identification  and  test,  by  filtering 
through  a  paper  filter,  as  the  oily  materials  remain  on  the  filter. 

Ordinary  commercial  rosin  (colophony),  and  the  resinous  material 
obtained  by  extracting  wood  pulp  with  ether,  and  engine  oil,  and 
10293°— Bull.  96—16 i 


46  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

crystalline  nitrosubstitution  compounds,  including  mononitronaph- 
thalene,  mononitrotoluene,  dinitrotoluene,  and  trinitrotoluene,  are  all 
soluble  in  nitroglycerin  to  an  extent  that  vitiates  the  determination 
of  nitrogen  in  the  filtered  nitroglycerin.  For  this  reason  the  nitro- 
glycerin obtained,  by  extraction  with  ether,  from  explosives  con- 
taining wood  pulp  shows  a  slightly  low  figure  for  nitrogen  content, 
even  when  the  small  proportion  of  resinous  substances  is  removed  by 
filtering. 

DETERMINATION  OF  SULPHUR  IN  THE  ETHER  EXTRACT. 

If  an  explosive  contains  sulphur,  some  of  the  sulphur  will  be  found 
in  the  ether  extract.  However,  as  sulphur  is  only  slightly  soluble 
in  ether,  it  is  advisable  to  make  an  additional  extraction  with  carbon 
bisulphide,  preferably  after  extracting  with  water,  in  order  to  insure 
complete  removal  of  the  sulphur. 

If  crystals  of  sulphur  are  noted  in  the  ether  extract,  the  procedure 
is  usually  as  follows : 

The  extract  from  which  all  ether  has  been  evaporated  is  poured 
from  the  beaker  into  a  dry  paper  filter  fitted  in  a  small  funnel,  and 
the  clear  liquid  (generally  nitroglycerin)  allowed  to  filter  through 
into  a  small  weighed  beaker.  A  convenient  amount  (approximately 
0.7  gram)  of  this  filtrate  is  used  for  a  determination  in  the  nitrometer 
to  ascertain  whether  it  is  pure  nitroglycerin  or  contains  other  liquid 
or  dissolved  ingredients.  A  nitrogen  content  of  18.30  per  cent  or 
more,  indicating  at  least  99  per  cent  of  nitroglycerin,  may  be  con- 
sidered as  denoting  freedom  from  any  other  liquid  or  dissolved 
material  in  appreciable  quantities. 

The  nitroglycerin  left  in  the  filter  is  completely  removed  by  wash- 
ing with  70  per  cent  acetic  acid,  leaving  the  sulphur  on  the  filter. 
Any  sulphur  in  the  beaker  that  originally  contained  the  extract  is 
also  transferred  to  the  filter  by  washing  with  acetic  acid.  The  sul- 
phur is  then  freed  from  acetic  acid  by  washing  with  water,  dried, 
and  weighed.  To  the  quantity  of  sulphur  thus  found  is  added  the 
quantity  found  later  by  extraction  with  carbon  bisulphide. 

DETERMINATION     OF     VASELINE,     PARAFFIN,     OILS,     AND     RESINS     IN     THE 

ETHER  EXTRACT. 

Vaseline,  paraffin,  oils,  and  similar  substances  in  the  ether  extract 
may  be  separated  from  the  nitroglycerin  by  the  method  that  is  used 
for  separating  the  sulphur,  namely,  by  dissolving  the  nitroglycerin, 
nitrotoluene,  etc.,  in  acetic  acid  (70  per  cent  pure)  and  collecting  the 
insoluble  substances  on  a  paper  filter,  from  which  they  may  be  again 
dissolved  by  means  of  ether,  the  ether  removed  by  evaporation,  and 
the  oily  material  weighed.  The  sulphur,  if  any,  will  be  left  on  the 


QUANTITATIVE  ANALYSIS.  47 

filter,  together  with  the  vaseline,  paraffin,  or  oil,  in  which  case  the 
oily  substances  may  be  extracted  from  the  sulphur  with  a  small 
quantity  of  ether  or  petroleum  ether,  in  both  of  which  sulphur  is 
only  slightly  soluble,  the  solvent  evaporated,  and  the  oily  substance 
weighed. 

Kesin,  if  present,  will  be  dissolved  by  the  acetic  acid  used  for  re- 
moving the  nitroglycerin  and  should  be  determined  in  a  separate 
part  of  the  ether  extract  by  titration  with  a  saturated  solution  of 
alcoholic  potash  °  or  by  saponifying  the  nitroglycerin  with  alcoholic 
potash,  acidifying,  and  weighing  the  separated  resin.& 

DETERMINATION    OF    NITROSUBSTITUTION    COMPOUNDS    IN    THE    PRESENCE 

OF    NITROGLYCERIN. 

A  satisfactory  method  for  the  separation  of  nitrosubstitution  com- 
pounds from  nitroglycerin  has  been  worked  out  in  the  explosives 
chemical  laboratory  of  the  Bureau  of  Mines  by  A.  L.  Hyde,6  assist- 
ant chemist. 

This  method  depends  on  the  differences  in  solubility  of  nitro- 
glycerin and  nitrosubstitution  compounds  in  carbon  bisulphide  and 
mixtures  of  acetic  acid  and  water.  Nitroglycerin  is  only  slightly 
soluble  in  carbon  bisulphide,  but  is  readily  soluble  in  mixtures  of 
acetic  acid  and  water,  whereas  most  of  the  nitro  compounds,  although 
not  readily  soluble  in  carbon  bisulphide,  are  more  soluble  in  it  than 
nitroglycerin  and  are  less  soluble  than  nitroglycerin  in  mixtures  of 
acetic  acid  and  water.  Carbon  bisulphide  and  mixtures  of  acetic  acid 
and  water  are  only  slightly  miscible.  Hence  nitroglycerin  and  a 
nitro  compound  may  be  partly  separated  by  shaking  the  mixture  with 
carbon  bisulphide  and  a  solution  of  acetic  acid  and  water,  allowing 
the  two  solvents  to  separate  into  two  layers  and  drawing  off  one  of 
the  layers.  The  carbon-bisulphide  layer  will  contain  the  greater 
proportion  of  nitrosubstitution  compound  and  the  acetic-acid  layer 
the  greater  proportion  of  nitroglycerin. 

The  method  devised  by  Hyde  involves  a  continuous  fractional 
separation  of  the  ingredients  of  such  mixtures.  The  following  de- 
scription of  the  apparatus  and  method,  as  in  use  in  the  explosives 
laboratory  of  the  bureau,  is  taken  from  Hyde's  paper.0 

DESCRIPTION   OF  APPARATUS. 

The  apparatus  consists  of  a  series  of  13  tubes  for  holding  the  2  solvents,  a 
circulating  system  made  of  glass  tubing,  a  flask,  which  may  be  heated  in  any 
convenient  manner,  at  one  end  of  the  system,  a  return  pipe  from  this  flask,  and 
a  measuring  device,  condenser,  and  reservoir  at  the  other  end  of  the  system. 

0  Snelling,  W.  O.,  and  Storm,  C-  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
51,  Bureau  of  Mines,  1913,  pp.  41-42. 

6  Hyde,  A.  L.,  The  quantitative  separation  of  nitrosubstitution  compounds  from  nitro- 
glycerin :  Jour.  Am.  Chem.  Soc.,  vol.  35,  September,  1913,  p.  1173. 

c  Hyde,  A.  L.,  loc.  cit, 


48 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


The  whole  is  mounted  in  a  wooden  frame  of  suitable  form  and  size,  as  shown 
in  figure  6. 

The  tubes  for  holding  the  solvents  are  made  in  the  form  shown.  The  main 
shank  has  an  inside  diameter  slightly  less  than  1  cm.  and  a  length  of  about  19 
cm.  The  top  and  bottom  parts  have  an  inside  diameter  of  about  2  cm.  The 
bottom  part  is  about  4  cm.  long,  the  top  part  about  6  cm.  The  top  of  each  tube 
is  closed  with  a  No.  3  two-hole  rubber  stopper. 


FIGURE  6. Apparatus  for  separation  of  nitrosubstitution  compounds  from  nitroglycerin. 

a,  Support ;  6,  reservoir ;  c,  condenser ;  d,  measuring  device ;  e,  collecting  flask ;  1  to  IS, 
tubes. 

The  circulating  system  consists  of  a  series  of  glass  tubes  of  a  size  to  fit 
snugly  the  holes  of  the  No.  3  stoppers,  and  bent  at  the  top  in  the  form  of  an 
inverted  U.  The  long  arm  of  each  tube  is  long  enough,  when  passed  through 
the  No.  3  stopper  and  the  stopper  is  tightly  inserted  in  the  reaction  tube,  tc 
reach  almost  to  the  bottom  of  the  reaction  tube.  The  short  arm,  about  6  cm 


QUANTITATIVE   ANALYSIS.  49 

long,  is  drawn  to  capillary  size  at  the  end.  The  long  arm  of  each  tube  Is 
passed  through  one  hole  of  a  rubber  stopper  and  the  short  arm  through  a  hole  of 
the  stopper  next  in  the  series  so  that  the  tubes  form  a  continuous  chain.  A 
tube  leading  from  the  reservoir  passes  through  the  first  stopper  of  the  series, 
and  a  tube  leading  from  the  bottom  of  the  last  reaction  tube  to  the  collecting 
flask  passes  through  the  last  stopper. 

The  bottom  of  the  collecting  flask  is  situated  about  30  cm.  lower  than  the 
bottom  of  the  reaction  tubes  in  order  that  a  siphon  may  be  formed  to  cause  a 
continuous  flow  of  liquid  through  the  tubes  into  the  flask.  Just  above  the  flask 
is  a  stopcock  designed  to  regulate  the  flow  through  the  siphon.  The  flask  has 
a  ground-glass  stopper  with  two  openings,  one  of  which  is  connected  with  the 
return  pipe  to  the  condenser. 

The  condenser  is  provided  with  a  siphon  measuring  device,  holding  80  c.  c., 
for  measuring  the  quantity  of  solvent  that  passes  through  the  system.  This 
measuring  device  empties  directly  into  the  reservoir  below.  The  whole  circu- 
lating system  is  fastened  in  the  wooden  stand  and  remains  there  permanently, 
but  the  reaction  tubes  may  be  removed  for  cleaning  and  filling.  When  the 
reaction  tubes  are  filled  and  in  place  the  whole  series  forms  an  air-tight  system. 

OPERATION  OF  THE  APPARATUS. 

To  use  the  apparatus,  tubes  2  to  11,  inclusive,  are  filled  up  to  the  bottom  of 
the  shank  with  carbon  bisulphide,  and  the  remainder  of  their  length  with  a  mix- 
ture consisting  of  75  per  cent  acetic  acid  and  25  per  cent  water.  About  170  c.  c. 
of  the  mixture  are  required  for  the  entire  apparatus.  The  mixture  should 
nearly  touch  the  stopper  when  the  tube  is  placed  in. the  system,  thus  allowing 
the  capillary  point  of  the  U-tube  to  dip  2  or  3  cm.  into  the  liquid.  Tubes  12 
and  13  are  filled  in  the  same  way,  but  with  water  instead  of  acetic-acid  mix- 
ture, and  are  intended  to  take  up  any  small  quantities  of  acetic  acid  carried 
along  with  the  carbon  bisulphide  from  the  other  tubes.  Except  for  this  precau- 
tion considerable  acetic  acid  would  be  carried  into  the  collecting  flask  and  cause 
delay  in  subsequent  evaporation. 

After  the  solvent  tubes  are  in  place  the  mixture  to  be  separated  is  dissolved 
in  10  to  15  c.  c.  of  a  mixture  of  acetic  acid  and  water,  and  the  solution  is 
poured  into  tube  1  on  top  of  the  layer  of  carbon  bisulphide  already  poured  into 
the  bottom  part  of  the  tube.  When  tube  1  is  in  place  carbon  bisulphide  is 
poured  into  the  measuring  device  until  it  runs  over  into  the  reservoir,  the  col- 
lecting flask  is  put  in  place,  and  the  process  is  started  by  opening  the  cock  just 
above  the  collecting  flask.  The  rate  of  flow  is  regulated  by  means  of  the  cock 
so  that  3  to  4  c.  c.  of  solvent  flows  into  the  flask  per  minute.  The  flask  is  heated 
by  immersing  it  in  a  dish  of  hot  water,  which  is  heated  by  a  small  electric 
heater. 

The  action  that  takes  place  is  as  follows:  Carbon  bisulphide  coming  down 
through  the  tube  from  the  reservoir  falls  in  fine  drops  through  the  acetic-acid 
solution  containing  both  nitroglycerin  and  the  nitro  compound,  extracts  some 
of  both,  and  carries  this  over  into  tube  2.  Here  the  carbon  bisulphide  again 
falls  through  the  acetic-acid  mixture  in  a  series  of  fine  drops,  and  most  of  the 
nitroglycerin  and  some  of  the  nitro  compound  are  extracted.  The  same  process 
is  repeated  in  each  reaction  tube,  the  solvent  stream  being  freed  more  and 
more  from  nitroglycerin  as  it  progresses  along  the  system.  After  a  certain 
quantity  of  carbon  bisulphide  has  passed  through  the  system,  nitro  compound, 
entirely  free  from  nitroglycerin,  begins  to  appear  in  the  stream  flowing  into 
the  collecting  flask.  If  suflicient  solvent  is  passed  through  the  system,  prac- 


50 


ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 


tically  all  of  the  nitro  compound  will  be  carried  over  into  the  collecting  flask. 
While  the  solvent  is  flowing  into  the  collecting  flask  it  is  also  being  evaporated 
and  passed  back  to  the  condenser  to  be  used  again.  After  the  process  is  com- 
pleted the  flask  is  removed,  the  solution  poured  into  a  small  beaker,  the  solvent 
evaporated  in  a  bell-jar  evaporator,®  and  the  nitro  compound  weighed. 

In  the  case  of  a  nitro  compound  much  more  soluble  in  carbon  bisulphide  than 
nitroglycerin  is,  practically  all  the  nitro  compound  will  have  passed  into  the 
collecting  flask  before  traces  of  nitroglycerin  appear  there.  In  case,  however, 
the  difference  in  solubility  is  slight,  small  quantities  of  nitroglycerin  will  begin 
to  appear  in  the  collecting  flask  before  all  the  nitro  compound  has  come. over. 
It  is  obvious  that  in  these  cases  a  perfectly  sharp  quantitative  separation  can 
not  be  made  with  a  single  fractionation,  but  even  in  these  cases,  as  will  be 
shown,  it  is  possible  to  obtain  satisfactory  results  with  a  single  fractionation  by 
regulating  the  quantity  of  solvent  passing  through  the  system. 

It  is  evident  that  with  a  nitro  compound  whose  solubility  is  only  slightly  dif- 
ferent from  that  of  nitroglycerin,  the  accuracy  of  the  separation  depends  upon 
stopping  the  process  after  most  of  the  nitro  compound  has  passed  over  and  before 
much  nitroglycerin  begins  to  pass  over. 

It  was  found  that  the  passage  of  about  880  c.  c.  of  carbon  bisulphide  through 
the  apparatus  sufficed  to  carry  over  practically  all  the  nitro  compound.  Three 
mixtures  were  tested  using  this  quantity  of  solvent.  The  results  are  noted 
below : 

Results  of  separation  of  nitrotoluenes  from  nitroglycerin. 


Mix- 
ture. 

* 
Components. 

Composition  of  mixture. 

Actual. 

By  analysis. 

Grams. 

Per  cent. 

Grams. 

Per  cent. 

1 
2 
3 

f  Nitroglycerin  

2.623 
2.353 
2.838 
1.631 
3.400 
.955 

52.7 
47.3 
63.5 
36.5 
78.1 
21.9 

2.595 
2.381 
2.831 
1.638 
3.406 
.949 

52.2 

47.8 
63.4 
36.6 

78.2 
21.8 

\"  Liquid  trinitrotoluene".  .  . 

/Nitroglycerin  

1"  Liquid  trinitrotoluene" 

JNitroglycerin  

\tf  L/iquicl  trinitrotoluene" 

In  order  to  determine  whether  any  nitroglycerin  was  present  in  the  product 
obtained  in  the  collecting  flask,  tests  were  made  in  several  of  the  foregoing 
experiments.  These  tests  showed  that  in  no  case  was  the  separation  entirely 
complete,  but  that  1  to  2  per  cent  of  the  quantity  of  nitroglycerin  originally 
present  had  passed  into  the  collecting  flask.  However,  as  the  above  results 
show,  the  accuracy  is  sufficient  for  most  purposes.  If  in  any  particular  case 
it  is  desired  to  obtain  the  nitro  compound  more  nearly  free  from  nitroglycerin 
than  can  be  obtained  with  one  separation,  a  second  separation  may  be  made, 
which  will  still  further  reduce  the  proportion  of  nitroglycerin.  But  this  is  a 
rather  tedious  process  and  usually  should  not  be  necessary.  A  double  separa- 
tion of  one  mixture  was  made  to  determine  what  accuracy  could  be  expected. 

The  mixture  contained  3.475  grams,  or  58.8  per  cent  of  nitroglycerin,  and 
2.434  grams,  or  41.2  per  cent  of  liquid  trinitrotoluene.  The  nitrotoluene  ob- 
tained after  two  separations  weighed  2.388  grams,  or  40.4  per  cent  of  the  orig- 
inal mixture.  A  test  of  the  nitrotoluene  separated  showed  that  it  contained 
less  than  10  mg.  of  nitroglycerin. 


0  For  description  of  evaporator  see  pp.  35  and  36  of  this  bulletin. 


QUANTITATIVE   ANALYSIS.  51 

Additional  experiments  showed  that  certain  other  nitrosubstitu- 
tion  compounds  besides  the  nitrotoluenes  could  be  readily  separated 
from  nitroglycerin  by  this  method ;  for  example,  mononitrobenzene, 
dinitrobenzene,  and  mononitronaphthalene,  and,  further,  that  various 
nitrosubstitution  compounds  may  be  just  as  readily  separated  from 
each  other,  the  only  requirement  being  that  there  shall  be  sufficient 
difference  in  their  solubilities. 

It  is  likely  that,  by  slight  changes  in  the  solvents  (for  example, 
in  the  strength  of  the  acetic  acid),  the  method  may  be  applied  to  the 
separation  of  any  nitrosubstitution  compounds  from  nitroglycerin 
or  from  each  other,  and  even  to  the  separation  of  oils  and  other 
ether-soluble  materials  from  nitroglycerin,  etc. 

DETERMINATION   OF    NITROPOLYGLYCERIN   IN    MIXTURE   WITH    NITRO- 
GLYCERIN. 

Some  types  of  low-freezing  explosives  contain  mixtures  of  nitro- 
glycerin and  nitropolyglycerin,  the  effect  of  the  latter  being  to 
greatly  reduce  the  freezing  point  of  the  nitroglycerin.  This  mix- 
ture is  usually  prepared  as  follows :  Glycerin  is  polymerized  by  one 
of  the  usual  methods,  generally  at  an  elevated  temperature  and  high 
pressure.  The  resulting  product  is  a  mixture  of  polymerized  gly- 
cerin and  unaltered  glycerin,  varying  in  composition  according  to 
the  length  and  conditions  of  treatment.  It  is  probable  that  the  poly- 
merized glycerin  contains  small  amounts  of  polymers  higher  than 
diglycerin. 

This  product  is  then  nitrated  in  the  same  manner  as  ordinary 
glycerin,  the  nitrated  material*  consisting  of  a  mixture  of  trinitro- 
glycerin,  tetranitrodiglycerin  and'  corresponding  nitrates  of  what- 
ever higher  polymers  may  be  present. 

This  mixture  is  in  appearance  and  general  properties  similar  to 
ordinary  nitroglycerin,  and  in  a  hasty  analysis  might  be  mistaken  for 
it.  The  best  means  of  identifying  the  nitropolyglycerin  are  by  (1) 
determination  of  nitrogen  content,  (2)  determination  of  molecular 
weight,  and  (3)  determination  of  solubility.  For  all  of  these  determi- 
nations the  residue  left  after  evaporation  of  the  ether  from  the  ether 
extract  should  be  filtered  in  order  to  remove  resins,  sulphur,  or  other 
substances  which  form  a  sort  of  scum  on  the  surface  of  the  liquid. 
A  small  filter  paper  in  a  small  funnel  can  be  used  for  the  filtration 
and  a  clear  liquid  is  easily  obtained. 

METHOD  FOE  DETERMINING  THE  NITROGEN   CONTENT  OF  THE   MIXTURE. 

In  determining  the  nitrogen  content  of  a  mixture  of  nitroglycerin 
and  nitropolyglycerin  by  means  of  the  nitrometer  about  0.75  gram 
of  the  filtered  ether  extract  is  used  for  the  determination.  The  nitro- 
gen content  of  pure  nitroglycerin  being  18.5  per  cent  and  that  of 


52  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

tetranitrodiglycerin  16.19  per  cent,  the  approximate  proportions  of 
these  two  compounds  in  the  mixture  are  readily  calculated  (any 
small  content  of  higher  polymers  being  disregarded). 

BOILING-POINT    METHOD    FOB    DETERMINING    MOLECULAB    WEIGHT    OF    THE    MIXTURE. 

For  determining  the  molecular  weight  of  a  mixture  of  nitroglyce- 
rin  and  nitropolyglycerin  the  boiling-point  method  has  been  found 
to  give  satisfactory  results,  ethyl  acetate  being  used  as  a  solvent.0 

The  apparatus  used  for  this  purpose  in  the  bureau's  laboratory  is  a 
slight  modification  of  the  well-known  Beckmann  apparatus.  The 
solution  is  heated  internally  by  means  of  an  electric  heating  coil  of 
fine  platinum  wire  sealed  into  the  bottom  of  the  tube,  and  in  order  to 
minimize  the  change  in  concentration  of  the  solution  a  condensing 
coil  of  copper  tubing  is  wrapped  around  the  outside  of  the  tube  just 
above  the  surface  of  the  solution.  Circulation  of  cold  water  through 
this  coil  keeps  the  walls  of  the  boiling  tube  cold  and  provides  for 
quick  condensation  of  the  vapors  of  the  solvent.  The  thermometer 
used  is  an  ordinary  Beckmann  differential  thermometer,  reading  to 
hundredths  of  a  degree. 

The  method  used  is  as  follows :  About  12  c.  c.  of  pure  ethyl  acetate 
is  placed  in  the  tube,  the  thermometer  inserted,  and  the  solvent  boiled 
until  equilibrium  is  established.  The  boiling  point  is  then  noted  and 
the  tube  is  emptied  and  dried.  A  weighed  quantity  of  the  mixture  to 
be  tested  (2.5  to  3  grams)  is  dissolved  in  about  10  c.  c.  of  the  ethyl 
acetate,  the  solution  is  then  weighed  and  quickly  transferred  to  the 
boiling-point  tube.  The  boiling  point  of  the  solution  is  determined 
under  the  same  conditions  as  that  of  the  pure  solvent ;  the  difference 
in  the  boiling  points  represents  the  effect  of  the  dissolved  material. 

Assuming  that  the  law  for  dilute  solutions  holds  also  in  the  case 
of  more  concentrated  solutions,  the  molecular  weight  of  the  substance 

is  m=^,  where  g  is  the  weight  in  grams  of  added  substance  per  100 

Cb 

grams  of  solvent,  a  the  rise  in  boiling  point,  and  r  the  boiling-point 
constant  of  the  solvent  used  (r=26.1  for  ethyl  acetate6). 

It  has  been  shown  by  Hyde c  that  excellent  results  may  be  obtained 
with  this  method  if  ethyl  acetate  be  used  as  the  solvent,  but  that 
results  with  ether,  acetone,  methyl  alcohol,  and  chloroform  are  not 
concordant  and  vary  rather  widely  with  the  concentration  of  the  solu- 
tion. Many  determinations  on  pure  nitroglycerin  by  this  method 
have  given  for  the  molecular  weight  values  ranging  from  229  to  235. 
The  theoretical  molecular  weight  is  227. 

a  Hyde,  A.  L.,  Boiling  points  of  solutions  of  nitroglycerin  :  Original  Communications, 
8th  Int.  Cong.  App.  Chem.,  vol.  4,  1912,  p.  59. 

bBiedemann,  R.,  Chemiker  Kalender,  1910,  vol.  2,  p.  49. 
c  Hyde,  A.  L.,  loc.  cit. 


QUANTITATIVE   ANALYSIS.  53 

THE    TWO    METHODS    COMPARED. 

In  order  to  test  the  value  of  this  method  in  comparison  with  the 
nitrometer  method,  a  sample  of  partly  polymerized  glycerin  was 
nitrated  and  washed  free  from  acid.  The  resulting  mixture  of  nitro- 
glycerin  and  nitropolyglycerin  was  found  by  test  in  the  nitrometer 
to  contain  16.85  to  16.88  per  cent  of  nitrogen.  Assuming  the  mix- 
ture to  consist  of  nitroglycerin  (18.50  per  cent  nitrogen)  and  tetra- 
nitrodiglycerin  (16.19  per  cent  nitrogen),  the  nitrogen  content  of 
the  mixture  corresponds  to  that  of  a  mixture  containing  29.23  per 
cent  nitroglycerin  and  70.77  per  cent  tetranitrodiglycerin.  Such  a 
mixture  would  have  a  molecular  weight  (calculated)  of  311.  The 
molecular- weight  determination  made  as  above  described  gave  results 
of  306  and  314,  an  average  of  310. 

A  second  sample  of  partly  polymerized  glycerin  was  nitrated  in  a 
similar  manner  and  the  nitrated  product  tested,  with  the  following 
results : 

The  nitrogen  content  was  16.58  to  16.63  (average  16.605)  per  cent, 
corresponding  to  a  mixture  consisting  of  17.75  per  cent  nitroglycerin 
and  82.25  per  cent  tetranitrodiglycerin.  The  calculated  molecular 
weight  of  this  mixture  is  325;  the  molecular  weight  as  determined 
was  325  and  328,  the  average  being  326.5. 

In  both  tests  the  results  of  the  determinations  of  nitrogen  and 
molecular  weight  agree  very  closely. 

METHOD   FOB    DETERMINING    SOLUBILITY   OF   THE    MIXTURE. 

The  difference  in  solubility  of  nitroglycerin  and  nitropolyglycerin 
in  dilute  acetic  acid  (60  volumes  of  glacial  acetic  acid  to  40  volumes 
of  water)  provides  a  convenient  means  of  identifying  nitropoly- 
glycerin in  such  a  mixture. 

Experiments  have  shown  that  1  gram  of  nitroglycerin  will  com- 
pletely dissolve  in  approximately  10.5  c.  c.  of  dilute  acetic  acid  of 
the  concentration  mentioned — the  specific  gravity  of  such  a  mixture 
is  approximately  1.069  at  15°  C. — whereas  nitropolyglycerin  is  much 
less  soluble.  One  gram  of  the  mixture  of  nitroglycerin  and  nitro- 
polyglycerin previously  mentioned  containing  82.25  per  cent  tetra- 
nitrodiglycerin required  120  c.  c.  of  the  acetic-acid  solution  to  com- 
•pletely  dissolve  it.  In  treating  this  sample  with  the  acetic  acid,  add- 
ing the  acid  in  small  quantities  and  shaking  thoroughly  after  each 
addition,  it  was  found  that  when  about  50  c.  c.  had  been  added  only  a 
small  quantity  of  the  mixture  remained  undissolved,  and  this  small 
quantity  required  about  70  c.  c.  more  acid  for  complete  solution,  the 
volume  of  the  undissolved  part  decreasing  slightly  with  each 
addition  of  10  c.  c.  of  acid. 

Although  no  definite  conclusions  as  to  the  presence  of  nitropoly- 
glycerin should  be  made  from  the  results  of  any  one  of  the  three 


54  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

tests  described,  it  is  apparent  that  the  data  supplied  by  all  three 
tests  when  combined  is  sufficient  to  determine  whether  there  is  any 
nitropolyglycerin  in  the  ether  extract. 

This  point  may  be  illustrated  by  the  following  description  of  an 
actual  analysis.  The  ether  extract  from  an  ammonium-nitrate  ex- 
plosive was  an  oily  liquid  with  the  appearance  of  nitroglycerin.  A 
filtered  part  of  this  extract  was  found  by  the  nitrometer  to  contain 
only  17.7  per  cent  nitrogen.  A  molecular-weight  determination  on 
another  part  gave  a  result  of  265,  indicating  a  mixture  with  a 
molecular  weight  greater  than  that  of  nitroglycerin.  About  5  grams 
of  the  extract  was  shaken  with  150  c.  c.  of  60  per  cent  acetic  acid 
(nearly  three  times  the  amount  necessary  to  dissolve  5  grams  of  pure 
nitroglycerin).  The  insoluble  part  was  separated,  washed,  dried, 
and  its  nitrogen  content,  determined  in  the  nitrometer,  was  16.24 
per  cent,  which  is  almost  the  theoretical  nitrogen  content  (16.19 
per  cent)  of  tetranitrodiglycerin. 

If  the  extract  is  composed  of  nitroglycerin  and  tetranitrodi- 
glycerin, the  nitrogen  content  of  17.7  per  cent  indicates  a  mixture 
consisting  of  65.4  per  cent  nitroglycerin  and  34.6  per  cent  tetranitrodi- 
glycerin, whereas  the  molecular  weight  265  indicates  a  mixture  con- 
taining 68  per  cent  nitroglycerin  and  32  per  cent  tetranitrodiglycerin. 
It  is  therefore  safe  to  assume  that  the  extract  consists  of  approxi- 
mately 2  parts  of  nitroglycerin  to  1  part  of  tetranitrodiglycerin. 

EXTRACTION   WITH   WATER. 

METHOD  OF  EXTRACTING  WATER-SOLUBLE  INGREDIENTS. 

In  practically  all  types  of  permissible  explosives  the  extraction 
with  water  is  carried  out  on  the  dried  and  weighed  residues  left  in 
the  extraction  crucibles  after  extracting  with  ether.  The  method 
employed  is  the  same  as  in  the  treatment  of  ordinary  dynamites.0 
The  Gooch  crucible  is  inserted  in  the  top  of  a  carbon  filter  tube,  which 
is  fitted  with  a  short  length  of  thin- walled  rubber  tubing  to  make  a 
tight  joint  between  the  crucible  and  the  filter  tube.  The  lower  end 
of  the  filter  tube  is  passed  through  a  rubber  stopper  in  the  mouth  of  a 
side-neck  suction  flask.  About  200  c.  c.  of  cold  distilled  water  is  then 
passed  through  the  sample  in  each  crucible  in  quantities  of  about 
20  c.  c.  each,  each  addition  of  water  being  allowed  to  stand  in  the 
crucible  for  a  short  time  before  it  is  drawn  into  the  flask.  The 
necessary  suction  is  obtained  from  an  ordinary  filter  pump  operated 
by  water  pressure.  A  few  drops  of  the  last  addition  of  water  passed 
through  the  sample  are  tested  by  evaporation  on  a  glass  plate  to 
insure  that  all  water-soluble  material  has  been  dissolved. 

0  See  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite : 
Bull.  51,  Bureau  of  Mines,  1913,  p.  43. 


QUANTITATIVE   ANALYSIS.  55 

If  the  qualitative  analysis  of  the  explosive  has  indicated  that  it 
contains  a  considerable  proportion  of  starch,  the  extractions  will  be 
facilitated  by  the  use  of  porous  alundum  filtering  crucibles  in  place 
of  the  ordinary  porcelain  Gooch  crucibles,  as  the  porous  crucibles 
permit  the  water  solution  to  filter  through  the  walls  of  the  crucible 
above  the  dense  layer  of  starch  which  will  separate  out  in  the  bottom 
of  the  crucible.  With  porous  crucibles,  however,  it  has  been  found 
advisable  to  use  the  Spencer  glass  funnel,a  which  provides  for  a  tight 
joint  between  the  top  of  the  crucible  and  the  walls  of  the  funnel  by 
means  of  a  soft  rubber  ring  resting  on  top  of  the  crucible.  By  means 
of  this  apparatus  the  absorption  of  water-soluble  salts  in  the  upper 
part  of  the  wall  of  the  crucible  is  avoided,  as  the  crucible  may  be 
entirely  filled  with  each  addition  of  water,  completely  removing  all 
soluble  material.  Perfect  washing  of  the  upper  part  of  the  porous 
crucibles  is  practically  impossible  when  the  ordinary  carbon  filter 
tubes  are  used. 

Another  device  which  has  been  found  to  insure  complete  removal  of 
the  water-soluble  material  from  the  porous  crucibles  is  the  so-called 
"filtering  crucible  holder,"  which  enables  the  porous  crucible  to  be 
used  with  any  ordinary  60-degree  funnel.  The  holder  consists  of  a 
hard-rubber  device  with  a  soft  flange  forming  tight  joints  with  the 
walls  of  the  funnel  on  one  side  and  with  the  extreme  top  of  the 
crucible  walls  on  the  other  side.  Both  of  the  above  devices  are  used 
in  the  explosives  laboratory  of  the  Bureau  of  Mines  and  give  satis- 
factory results. 

The  water  extracts  are  transferred  from  the  suction  flasks,  diluted 
with  distilled  water  to  a  known  volume,  usually  250  c.  c.  each,  and 
reserved  in  stoppered  bottles  for  quantitative  determination  of  the 
dissolved  ingredients. 

DRYING  OF  INSOLUBLE  RESIDUE. 

The  crucibles,  after  the  contents  have  been  subjected  to  extraction 
with  water,  are  placed  in  a  drying  oven  and  the  residue  dried  to 
constant  weight.  About  five  hours'  drying  at  a  temperature  of  95° 
to  100°  C.  is  usually  necessary  for  thorough  drying  of  the  residue, 
especially  if  it  contains  wood  pulp,  cereal  products,  or  other  organic 
materials,  and  it  is  often  convenient  to  continue  the  drying  for  a 
longer  period,  for  example,  overnight.  Upon  removal  from  the  oven 
the  crucibles  with  their  contents  are  placed  in  a  tight  desiccator, 
preferably  over  sulphuric  acid,  and  weighed  as  soon  as  they  have 
cooled  to  room  temperature,  about  15  to  20  minutes  being  sufficient 
for  cooling. 

a  Spencer,  G.  L.,  Alundum  crucibles  in  gravimetric  analyses  :  Jour.  Ind.  Eng.  Chem., 
vol.  4,  1912,  p.  614. 


56  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

The  loss  of  weight  noted  represents  the  total  amount  of  water- 
soluble  material,  including,  in  addition  to  all  water-soluble  salts  and 
soluble  organic  ingredients,  small  quantities  of  substances  extracted 
from  the  wood  pulp,  cereal  products,  or  other  carbonaceous  ab- 
sorbents. 

EXAMINATION  OF  WATER  EXTRACT. 

It  has  been  noted  in  the  table  of  possible  components  shown  on 
page  13  that  the  water  extract  of  a  low-flame  explosive  may  contain  a 
great  variety  of  constituents,  and  attention  has  been  called  on 
page  17  to  the  difficulties  often  involved  in  definitely  determining 
the  manner  in  which  the  various  bases  and  acid  radicles  were  ac- 
tually combined  in  the  original  explosive. 

When  qualitative  tests  have  been  obtained  for  several  water-soluble 
ingredients,  the  method  of  mechanical  examination  (p.  17)  or  that 
of  specific-gravity  separation  (p.  18)  may  give  information  as  to 
exactly  what  combination  of  salts  is  present,  so  that  the  results  of  the 
separate  determinations  of  bases  and  acid  radicles  may  be  properly 
interpreted. 

The  analysis  of  the  water  solution  may  involve  many  determina- 
tions which  can  be  carried  out  by  well-known  methods  described 
in  reliable  textbooks  on  quantitative  analysis,  such  as  the  determina- 
tion of  chloride  by  precipitation  as  AgCl,  of  sulphate  by  precipi- 
tation as  BaSO4,  of  oxalate  by  precipitation  as  CaC2O4  and  igni- 
tion to  CaO,  of  carbonate  by  titration  or  evolution  methods,  or  of 
potassium,  magnesium,  calcium,  barium,  zinc,  and  aluminum,  by 
well-known  gravimetric  methods.  These  usual  methods  are  em- 
ployed in  the  bureau's  laboratory,  but  are  not  discussed  in  this 
bulletin  except  where  it  is  desired  to  emphasize  some  important 
feature. 

It  is  customary  to  determine  each  constituent  on  a  separate  aliquot 
part  of  the  water  extract;  usually  50  c.  c.  is  taken  for  each  deter- 
mination. Duplicate  analyses  are  made  on  parts  of  the  two  solu- 
tions representing  the  water  extracts  of  the  duplicate  samples  of  the 
explosives. 

DETERMINATION  OF  NONVOLATILE  SOLIDS. 

Aliquot  50  c.  c.  portions  of  the  water  extracts  are  evaporated  to 
dryness  in  weighed  platinum  dishes  on  a  steam  bath,  after  about 
1  or  2  c.  c.  of  nitric  acid  has  been  added.  If  the  solution  contains 
sulphates,  sulphuric  acid  is  added  instead  of  nitric.  Also,  if  more 
than  a  small  amount  of  chlorides  is  present,  the  evaporation  with 
nitric  acid  should  be  carried  out  not  in  platinum  dishes  but  in 
porcelain  or  silica  dishes,  because  of  the  fact  that  chlorine  liberated 
by  the  action  of  the  nitric  acid  on  chlorides  will  attack  the  platinum. 


QUANTITATIVE  ANALYSIS.  57 

Dishes  of  pure  fused  silica  ("Vitreosil"  or  other  commercial  prod- 
uct), about  3J  inches  in  diameter,  weighing  25  to  30  grams,  are 
largely  used  in  the  bureau's  laboratory  and  give  satisfactory  results. 

IGMTION   OF   EESIDUE. 

The  residue  from  the  evaporation  is  heated  gently  over  a  burner 
to  volatilize  ammonium  salts  and  free  acid,  and  burn  off  soluble 
organic  matter.  If  the  explosive  contains  organic  materials  such 
as  wood  pulp  or  cereal  products,  an  appreciable  quantity  of  soluble 
organic  material  will  be  found  in  the  water  solution.  Experiments 
in  the  bureau's  laboratory  have  shown  that  extraction  with  cold 
water  may  remove  as  much  as  2  to  3  per  cent  from  corn  meal,  10  to  15 
per  cent  from  wheat  flour  (middlings),  and  2  to  3  per  cent  from 
wood  pulp.  The  water  extract,  therefore,  may  contain  an  amount, 
which  depends  on  the  proportion  of  carbonaceous  material  in  the 
explosive,  of  dissolved  organic  material  varying  from  a  few  tenths 
of  1  per  cent  to  as  much  as  2  or  3  per  cent,  and  also  such  soluble 
organic  materials  as  are  actual  ingredients  of  the  explosive. 

After  gentle  ignition  the  residue  is  again  treated  with  a  small  quan- 
tity of  dilute  acid,  evaporated  to  dryness,  and  gently  ignited  until 
fuming  ceases,  or  heated  in  an  oven  at  about  120°  C. 

TREATMENT   OF   RESIDUE   CONTAINING   ZINC. 

If  the  original  sample  of  explosive  contained  ammonium  nitrate 
and  zinc  oxide,  the  zinc  oxide  will  have  been  mostly  dissolved  in  the 
water  solution  by  the  action  of  the  ammonium  nitrate,  and,  in  case 
nitric  acid  has  been  added  to  the  water  solution,  the  zinc  will  be 
present  as  zinc  nitrate  in  the  residue  left  on  evaporation.  The  zinc 
nitrate  is  readily  converted  by  ignition  to  zinc  oxide,  and  on  heating 
the  residue  strongly  an  evolution  of  oxides  of  nitrogen  accompanied 
by  an  appreciable  bubbling  of  the  fused  residue  is  noted.  This  bub- 
bling may  occasion  loss  of  the  fused  solids  unless  the  heating  is  done 
with  great  care.  It  is  therefore  advisable  not  to  attempt  to  convert 
the  zinc  nitrate  to  zinc  oxide  by  ignition,  but  to  leave  it  as  zinc 
nitrate,  by  heating  the  residue  just  to  its  fusion  point  only,  or 
heating  it  in  an  oven  at  about  120°  C.  for  one  hour.  Either  method 
will  completely  remove  the  free  acid  and  leave  the  residue  in  the 
form  of  nitrates. 

If  sulphuric  acid,  instead  of  nitric  acid,  has  been  added  to  the 
water  solution  during  evaporation,  the  evaporated  residue  will,  on 
heating  until  fumes  are  no  longer  given  off,  remain  as  sulphates. 

This  treatment  with  acid,  evaporation,  and  ignition  or  drying  is 
repeated  until  the  weight  of  residue  is  practically  constant.  The 
residue  represents  the  total  quantity  of  nonvolatile  inorganic  salts 


58  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

in  the  water  solution,  in  the  form  of  nitrates  or  sulphates,  depend- 
ing on  the  method  followed. 

The  value  of  this  determination  is  obvious.  For  example,  if  the 
solution  contained  sodium  nitrate,  ammonium  nitrate,  zinc  oxide, 
and  sodium  sulphate,  the  nonvolatile  residue  would  contain  Na2SO4 
and  ZnSO4.  The  use  of  the  specific-gravity  separation  in  the  pre- 
liminary qualitative  examination  (p.  18)  would  easily  have  indicated 
the  presence  of  sodium  sulphate  and  sodium  nitrate.  The  Na2SO4 
is  determined  gravimetrically  as  BaSO4  in  an  aliquot  part  of  the 
water  extract.  The  nonvolatile  residue  obtained  by  evaporation  of 
the  water  extract  is  redissolved,  the  zinc  determined  by  precipitation 
as  ZnCO3  and  ignition  to  ZnO,  and  this  weight  of  ZnO  calculated  to 
an  equivalent  weight  of  ZnSO4.  The  weight  of  Na2SO4  found  plus 
the  weight  of  ZnSO4  is  then  deducted  from  the  total  wreight  of 
residue  found  by  evaporation  as  sulphates,  the  difference  being  equal 
to  the  NaNO3  content  in  terms  of  Na2SO4.  The  equivalent  amount 
of  NaNO3  is  then  readily  calculated.  The  NH4NO3  in  the  water 
extract  is  then  determined  by  using  another  aliquot  portion  of  the 
solution,  and  should  be  approximately  equal  to  the  total  weight 
of  water-soluble  material  minus  the  sum  of  the  Na2SO4,  NaNO3, 
and  ZnO  contents,  unless  the  extract  contains  an  appreciable  amount 
of  soluble  organic  material. 

DETERMINATION  OF  AMMONIUM  SALTS  AS  NH3. 

Ammonium  salts  are  determined  by  the  well-known  method  of  dis- 
tillation. An  excess  of  strong  KOH  solution  is  added  to  an  aliquot 
part  of  the  water  extract  in  a  Kjeldahl  or  other  distillation  flask, 
the  NH3  is  distilled  into  a  known  volume  of  standard  H2SO4  solu- 
tion, and  the  excess  of  acid  titrated  with  standard  alkaline  solution, 
cochineal  being  used  as  the  indicator.  This  method  has  been  pre- 
viously described  in  Bulletin  51. a 

DETERMINATION    OF    ZINC. 

As  has  been  previously  stated,  when  an  explosive  contains  both  zinc 
oxide  and  ammonium  nitrate  the  zinc  will  be  found  mostly  in  the 
water  extract,  due  to  the  solubilitv  of  the  zinc  oxide  in  ammonium 
nitrate. 

The  residue  obtained  by  evaporation  of  the  water  extract  is  redis- 
solved in  dilute  HC1,  and  the  zinc  precipitated  as  ZnCO3  by  carefully 
adding  Na2CO3  until  a  slight  turbidity  shows  on  stirring.  The  mix- 
ture is  then  heated  to  boiling  and  filtered  while  hot  through  a  Gooch 
crucible.  If  the  solution  is  not  alkaline  after  boiling,  as  may  be 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull, 
51,  Bureau  of  Mines,  1913,  pp.  58-59, 


QUANTITATIVE   ANALYSIS.  59 

readily  determined  by  adding  a  few  drops  of  phenolphthalein  solu- 
tion, more  Na2CO3  is  added  until  the  red  color  of  the  indicator 
persists.  The  ZnCO2  in  the  Gooch  crucible  is  then  ignited  to  ZnO 
and  weighed. 

Other  alternative  methods  for  determining  zinc  have  been  described 
in  Bulletin  51,a  but  the  above  method  has  been  found  entirely  satis- 
factory. 

DETERMINATION  OF  POTASSIUM. 
PEBCHLOKATE  METHOD. 

Potassium  is  determined  by  the  well-known  method  of  precipita- 
tion with  platinic  chloride  or  by  the  perchlorate  method  of  Serullas.6 
The  perchlorate  method  depends  upon  the  fact  that  potassium  per- 
chlorate is  practically  insoluble  in  alcohol,  whereas  the  perchlorates 
of  the  other  bases  which  might  be  present  are  more  or  less  readily  dis- 
solved by  this  solvent. 

The  water  solution  containing  potassium  salts  must  be  free  from 
sulphuric  acid  or  sulphates ;  if  it  does  contain  them  they  can  be  re- 
moved by  precipitation  with  BaCl2  and  filtration.  The  solution  is 
then  evaporated  to  dryness  and  all  acid  fumes  and  ammonium  salts 
driven  off.  The  residue  is  dissolved  in  50  c.  c.  of  hot  water  contain- 
ing considerably  more  than  enough  perchloric  acid  to  combine  with 
all  the  bases.  Usually  5  to  6  c.  c.  of  perchloric  acid  solution  of  1.12 
specific  gravity  io  sufficient.  This  solution  is  obtainable  from  chemi- 
cal dealers  or  may  be  prepared  in  the  laboratory.0  Evaporate  the 
mixture  until  it  is  thick,  add  a  little  more  hot  water  and  5  to  6  c.  c. 
more  of  the  perchloric  acid,  and  continue  the  evaporation,  with  stir- 
ring. Then  heat  the  residue  on  a  sand  bath  until  dense  white  fumes 
are  evolved.  The  cooled  residue  is  then  stirred  with  20  c.  c.  of  97  per 
cent  alcohol  containing  0.2  per  cent  by  weight  of  perchloric  acid,  and 
transferred  to  a  Gooch  crucible,  using  20  c.  c.  more  of  the  same  alcohol 
solution.  The  residue  of  potassium  perchlorate  in  the  Gooch  crucible 
is  then  washed  with  about  20  c.  c.  of  a  mixture  of  equal  volumes  of 
ether  and  alcohol,  dried  at  120  to  130°  C.,  and  weighed. 

The  barium  perchlorate  is  readily  soluble  in  the  alcohol  used,  and 
magnesium  does  not  interfere  if  the  excess  of  perchloric  acid  is  large 
enough.  Ammonium  salts  should  be  removed,  as  has  been  stated,  be- 
cause ammonium  perchlorate  is  not  readily  soluble  in  alcohol. 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
51,  Bureau  of  Mines,  1913,  p.  58. 

6  Se"rullas,  — ,  Crystallization  de  1'acide  oxichlorique  (perchlorique),  et  sur  quelques 
proprietes  nouvelles  de  cet  acide  :  Ann.  chim.  phys.,  t.  46,  1831,  p.  294  ;  see  also  Wiley, 
H.  W.,  Principles  and  practice  of  agricultural  analysis,  vol.  2,  1908,  pp.  578-593. 

c  See  Willard.  II.  II.,  Preparation  of  perchloric  acid  :  Jour.  Am.  Chem.  Soc.,  vol.  34, 
1912,  pp.  1480-1485  ;  and  Kreider,  D.  A.,  The  preparation  of  perchloric  acid  and  Its 
application  to  the  determination  of  potassium :  Am,  Jour,  Sci.,  ser.  3,  vol.  49,  1895, 
p.  443. 


60 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES 


The  method  has  been  employed  in  the  bureau's  laboratory  with 
good  results  and  is  more  convenient  than  the  platinic  chloride  method. 

The  following  results  are  given  as  an  example  of  the  accuracy  of 
the  method  and  to  show  that  the  presence  of  sodium  nitrate  does  not 
interfere  with  the  determination  of  the  potassium  salt. 

Results  of  determination  of  potassium  nitrate  in  presence  of  sodium  nitrate 

by  perchlorate  method. 


Weight  of  KNO3  and 
NaN03  used. 

Weight  of 
KC104 
obtained. 

Weight  of 
KN03 
found. 

Error  of 
determina- 
tion. 

KNO3. 

NaN03. 

Gram. 
0.  2500 
.2500 

Gram. 
0.  2500 
.2500 

Gram. 
0.  3414 
.3420 

Gram. 
0.  2491 
.2495 

Gram. 
-0.  0009 
-.0005 

DETERMINATION  OF  NITRATES  BY  NITROMETER  METHOD. 

Nitrates  in  the  water  solution  may  be  determined  by  means  of  the 
nitrometer  as  described  in  Bulletin  51.a  An  aliquot  part  of  the  water 
solution,  containing  not  more  than  the  nitrogen  equivalent  of  0.8 
gram  of  NaNO3  or  1  gram  of  KNO3,  is  evaporated  nearly  to  dryness 
on  the  steam  bath  and  completely  transferred,  by  means  of  as  little 
water  as  possible,  to  the  nitrometer  generating  bulb.  Then  30  to  40 
c.  c.  of  95  to  96  per  cent  H2SO4  is  added  slowly  in  small  quantities  to 
avoid  overheating,  and  the  generator  shaken  8  to  10  minutes,  when 
the  volume  of  gas  (NO)  is  measured  and  the  percentage  of  nitrate 
calculated.  It  is  necessary  to  use  a  larger  volume  of  H2SO4  and  to 
shake  longer  than  is  required  in  the  determination  of  nitroglycerin 
because  of  the  dilution  of  the  acid  by  the  water  used  for  transferring 
the  sample  from  the  dish  to  the  generator.  The  method  gives  accu- 
rate results  if  care  is  taken  to  insure  tha.t  the  reaction  in  the  ni- 
trometer is  complete,  by  shaking  for  a  sufficient  length  of  time. 

DETERMINATION  OF  NITRATES  BY  NITRON   METHOD. 

The  determination  of  nitrates  by  the  "  nitron  "  method  of  Busch 6 
has  been  described  in  a  number  of  textbooks c  but  has  not  found  gen- 
eral use  in  technical  laboratories.  It  gives  very  reliable  results  when 
carried  out  with  proper  care  and  is  here  described  in  detail. 

"  Nitron,"  or  1:4  diphenyl  3 : 5  endoanilodihydrotriazol 
(C20H16N4),  forms  an  addition  product  with  one  molecule  of  HNO3 
which  is  only  slightly  soluble  in  cold  water. 

0  Snelling,  W.  O.,  and  Storm,  C.  G.,  The  analysis  of  black  powder  and  dynamite :  Bull. 
51,  Bureau  of  Mines,  1913,  p.  45. 

6  Busch,  M.,  Gravimetrische  Bestimmung  der  Salpetersaure  :  Ber.  deut.  chem.  Gesell. 
Jahrg.  38,  1905,  p.  861 ;  Gutbier,  A.,  Die  gewichtsanalytische  Bestimmung  der  Salpeter 
saure  mittels  "Nitron"  nach  M.  Busch:  Ztschr.  angew.  Chem.,  Jahrg.  18,  1905,  p.  494 
Hes  A.,  Uber  die  gewichtsanalytische  Bestimmung  der  Salpetersaure  :  Ztschr.  anal.  Chem. 
Jahrg.  48,  1909,  p.  81. 

cEscales,  R.,  Die  Schiessbaumwolle,  1905,  p.  218;  Lunge,  G.,  and  Berl,  E.,  Chemisch- 
technische  Untersuchungsmethoden,  Bd.  1,  1910,  p.  391. 


QUANTITATIVE   ANALYSIS.  61 


PREPARATION    OF    REAGENT. 


To  prepare  the  reagent,  1  part  of  nitron  is  dissolved  in  9  parts 
of  5  per  cent  acetic  acid  with  the  aid  of  heat,  filtered,  and  placed  in 
a  dark  bottle.  The  solution  decomposes  in-  the  light  and  does  not 
keep  well,  hence  it  is  best  to  prepare  it  in  small  quantities  as  needed. 

METHOD   OF   PROCEDURE. 

To  the  solution*  of  nitrate,  containing  preferably  not  over  0.10  to 
0.15  gram  of  nitrate,  diluted  to  about  80  c.  c.,  add  12  to  15  drops  of 
dilute  H2SO4,  heat  to  the  boiling  point,  add  12  to  15  c.  c.  of  the  nitron 
reagent,  stir  and  let  stand  one-half  to  three-fourths  hour.  Long, 
silky,  needlelike  crystals  of  the  nitron  nitrate  separate  out  on  cooling. 
Place  the  beaker  in  ice  water  for  one  to  two  hours  and  then  filter  off 
the  crystals  in  a  Gooch  crucible,  using  slight  suction.  Wash  with  10 
c.  c.  of  water  cooled  to  0°  C.,  and  added  in  quantities  of  1  to  2  c.  c.  at 
a  time,  using  a  part  of  the  filtrate  for  washing  out  the  beaker.  Dry 
the  precipitate  at  105°  to  110°  C.  until  constant  weight  is  obtained; 
about  one  hour  is  usually  sufficient.  To  insure  complete  precipita- 
tion the  filtrate  is  heated  to  boiling,  a  little  more  of  the  reagent  added, 
and  the  mixture  cooled  as  before. 

The  molecular  Aveight  of  nitron*  is  312,  of  nitron  nitrate  375.  Thus, 
the  nitrate  being  six  times  as  heavy  as  HNO3,  an  error  in  the  weight 
of  the  precipitate  is  reduced  to  one-sixth  when  expressed  as  HNO3 
or  to  one- twenty- seventh  when  expressed  as  N. 

The  equation  for  converting  the  weight  of  nitron  nitrate  to  the 
equivalent  weight  of  sodium  nitrate  is  as  follows : 

Weight  of  nitron  nitrate  X  85 =Weight  of  ^ium  nitrate. 
o75 

INTERFERENCE  OF  OTHER  SALTS. 

Busch0  states  that  moderate  amounts  of  chlorides  or  sulphates  do 
not  interfere  with  the  determination  of  nitrate,  but  that  bromides 
(solubility  1:800),  iodides  (1:20,000),  chromates  (1:6,000),  chlo- 
rates (1:4,000),  and  perchlorates  (1:50,000)  are  precipitated  by  the 
nitron  reagent. 

SOLUBILITY  OF  NITRON  NITRATE. 

Collins 6  found  that  0.45  per  cent  of  the  nitron-nitrate  precipitate 
dissolved  in  10  c.  c.  of  ice  water.  The  writer  has  found  that  if  the 
weighed  precipitate  from  0.15  gram  of  KNO3  is  treated  in  the  Gooch 
crucible  with  10  c.  c.  of  ice  water  in  the  same  manner  as  in  washing, 

a  Busch,  M.,  loc.  cit. 

»  Collins,  S.  W.,  The  "  nitron  "  method  for  the  estimation  of  nitric  acid  :  Analyst,  vol. 
82,  1907,  p.  349. 

10293°— Bull.  96—16 5 


62  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

an  average  loss  of  0.61  per  cent  results.  This  agreed  closely  with  the 
average  result  of  99.4  per  cent  obtained  in  determinations  of  pure 
KN03. 

RECOVERY   OF   NITRON. 

The  excess  nitron  in  the  filtrates  and  washings  and  the  nitron  con- 
tained in  the  precipitated  nitron  nitrate  may  be  recovered  as  follows : 

The  filtrates  and  washings  are  made  slightly  alkaline  with  NH4OH 
and  the  precipitated  nitron  filtered  and  washed  with  water.  The 
nitron-nitrate  precipitate  is  added  to  dilute  NH4OH,  warmed  to  60° 
C.,  the  precipitated  nitron  quickly  filtered  under  slight  pressure, 
washed  with  cold  water,  and  dried  in  a  vacuum.  Decomposition  may 
be  avoided  by  conducting  the  filtering  and  washing  in  an  atmosphere 
of  inert  gas  and  as  much  as  possible  away  from  the  light. 

DETERMINATION   OP   CHLORATES. 

Two  methods  for  the  determination  of  chlorates  are  employed  in  the 
bureau's  explosives  laboratory,  both  giving  excellent  results  and  offer- 
ing numerous  advantages  over  many  of  the  more  laborious  methods 
described  in  the  literature  and  in  the  textbooks. 

DETERMINATION   OF   CHLORATE  BY  REDUCTION   WITH    SULPHUR  DIOXIDE. 

Sulphur  dioxide  readily  reduces  chlorate  to  chloride  in  water  solu- 
tion. Its  use  in  quantitatively  determining  chlorate  is  briefly  men- 
tioned by  Gody,°  but  no  reference  to  it  has  been  found  by  the  writer 
in  any  textbook  on  analytical  methods. 

The  method  is  as  follows :  An  aliquot  part  of  the  water  extract  of 
an  explosive,  preferably  containing  not  more  than  about  0.50  gram 
of  chlorate,  is  treated  with  a  current  of  gaseous  sulphur  dioxide — 
which  may  be  conveniently  obtained  from  small  cylinders  of  liquid 
sulphur  dioxide,  from  which  the  current  of  gas  can  easily  be  regu- 
lated by  means  of  a  valve — until  a  strong  odor  of  the  gas  persists 
in  the  solution  after  stopping  the  current  and  blowing  across  the 
surface  of  the  liquid.  The  reduction  of  the  chlorate  is  accompanied 
by  a  slight  rise  in  temperature  of  the  liquid,  a  strong  solution  of 
chlorate  becoming  quite  warm  if  the  sulphur-dioxide  current  is  rapid. 
After  complete  saturation  with  sulphur  dioxide  the  liquid  is  boiled 
to  remove  any  excess  of  it.  It  is  advisable,  even  when  its  odor  is 
no  longer  noted,  to  insure  its  complete  removal  by  adding  a  few  cubic 
centimeters  of  hydrogen-peroxide  solution,  which  oxidizes  the  last 
traces  of  SO2  to  H2SO4.  The  solution  is  then  treated  with  a  few 
drops  of  nitric  acid  and  the  chloride  resulting  from  reduction  of  the 
chlorate  is  determined  in  the  usual  manner  by  precipitation  with 

°Gody,  L.,  Traite  theorique  et  pratique  des  matures  explosives,  1907,  p.  245. 


QUANTITATIVE   ANALYSIS. 


63 


silver  nitrate,  and  weighing  as  AgCl.  The  accuracy  of  the  method 
is  shown  by  the  following  results  on  weighed  quantities  of  pure 
potassium  chlorate. 

Results  of  determinations  of  pure  potassium  chlorate  by  SO2-r eduction  method. 


KC103 

found. 

Test  No. 

KC1O3 
used. 

AgCl 
found. 

Weight. 

Proportion 
of  original 
quantity. 

1  

Gram. 
0.2500 

Gram. 
0.2917 

Gram. 
0.2494 

Per  cent. 
99.76 

2    

.2500 

.2918 

.2495 

99.80 

3 

.2500 

.2915 

.2492 

99.68 

4  

.2500 

.2919 

.2496 

99.84 

Average 

99.71 

It  must  be  noted  that  the  complete  removal  of  the  sulphur  dioxide 
from  the  solution  is  necessary  in  order  to  avoid  reduction  of  the  silver 
nitrate. 

DETERMINATION    OF    CHLORATE    BY    REDUCTION     WITH    FORMALDEHYDE. 

Formaldehyde  in  the  form  of  the  commercial  solution  called 
"formalin,"  containing  approximately  40  per  cent  of  gaseous  for- 
maldehyde, is  also  an  effective  and  convenient  reducing  agent  for 
quantitatively  converting  chlorate  to  chloride.  Griitzner0  called 
attention  to  the  reduction  of  potassium  chlorate  by  means  of  for- 
maldehyde, and  noted  that  the  method  might  be  employed  for  the 
quantitative  determination  of  chlorates.  The  same  reaction  was  dis- 
covered independently  by  the  writer  in  1911  and  developed  into  an 
exact  quantitative  method  for  determining  chlorates  before  the  refer- 
ence to  Griitzner's  method  had  been  noted.  The  results  of  the  investi- 
gation of  this  method  will  be  published  as  a  separate  paper,  but  the 
following  brief  description  of  the  method  will  serve  to  indicate  its 
application  in  the  determination  of  chlorates  in  explosive  mixtures. 

A  part  of  the  water  extract  of  the  explosive,  containing  about  0.5 
gram  of  chlorate,  is  diluted  to  about  150  c.  c.  and  treated  with  5  to 
10  c.  c.  of  a  40  per  cent  solution  of  formaldehyde,  2  c.  c.  of  dilute 

nitric  acid   (1:3),  and  50  c.  c.  of  approximately  —  silver  nitrate 

solution.  The  beaker  containing  the  mixture  is  covered  with  a  watch 
glass  and  heated  on  the  steam  bath  for  3J  to  4  hours,  after  which  the 
precipitated  silver  chloride  may  be  at  once  filtered  off,  washed,  dried, 
and  weighed.  The  period  of  heating  on  the  steam  bath  may  be 

«  Griitzner,  B.,  Ueber  Formaldehyd  als  Reduktionsmittel  und  iiber  eine  neue  quantita- 
tive massanalytische  Bestimmung  desselben.  (A  volumetric  or  gravimetric  method  for  the 
determination  of  formaldehyde)  :  Arch.  Pharm.,  Bd.  234,  1896,  p.  634 ;  Ztschr.  anal. 
Chern.,  Jahrg.  36,  1897,  p.  527. 


64 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


shortened  to  2  hours  if  the  mixture  is  afterwards  allowed  to  stand 
overnight  before  filtering.  Boiling  the  solution  causes  loss  of  some 
chlorine  compound  and  makes  the  results  low. 

The  following  tabulation  of  a  few  results  taken  at  random  from  a 
large  number  of  tests  made  as  described  above  shows  that  the  method 
gives  remarkably  accurate  results. 

Results  of  determinations   of  pure  potassium  chlorate   by   the  formaldehyde 

reduction  method. 


Test  No. 

Weight  of 
KC103 
used. 

Weight  of 
AgCl 
found. 

KC1O3  found. 

Weight. 

Proportion 
of  original 
quantity. 

1                              

Gram. 
0.5002 
.5003 
.5002 
.5004 
.5002 
.5000 
.5003 

Gram. 
0.5855 
.5850 
.5841 
.5850 
.5848 
.5840 
.5850 

Gram. 
0.5006 
.5002 
.4994 
.5002 
.5000 
.4993 
.5002 

Per  cent. 
100.08 
99.98 
99.84 
99.95 
99.96 
99.86 
99.98 

2                  

3                               

4                                                     

5                             

g                                                     

7  

99.95 

DETERMINATION  OF  PERCHLORATES. 


Several  methods  for  the  determination  of  perchlorates  have  been 
investigated  in  the  explosives  laboratory  of  the  bureau,  and  the 
fusion  method  and  the  nitron  method  have  been  selected  as  the  most 
convenient  and  satisfactory. 


FUSION    METHOD. 


The  fusion  method  consists  in  converting  the  perchlorate  to  chlo- 
ride by  fusion  with  anhydrous  sodium  carbonate  and  determining  the 
resulting  chloride  by  the  usual  method  of  precipitation  as  silver 
chloride.0 

To  determine  the  perchlorate  in  a  water  solution,  an  aliquot  part 
of  the  solution  is  evaporated  to  a  small  volume  and  completely 
transferred  to  a  25-c.  c.  platinum  crucible,  where  evaporation  is 
continued  until  the  volume  is  about  5  c.  c.  Anhydrous  sodium  car- 
bonate is  then  added  to  the  solution  in  the  crucible  until  the  crucible 
is  completely  full  of  the  powder.  The  small  amount  of  solution  is 
absorbed  by  the  sodium  carbonate,  and  is  readily  dried  out  by  careful 
heating  with  a  small  flame  or  on  a  steam  bath  or  hot  plate,  after 
which  the  mass  is  heated  over  a  burner  until  no  evolution  of  gas 
bubbles  is  noted.  The  time  of  fusion  is  usually  15  to  20  minutes. 
The  melt  is  then  cooled,  dissolved  in  dilute  nitric  acid,  and  the  chlo- 
ride determined  by  precipitation  with  silver  nitrate. 

"Forster,  O.,  Mittheilungen  aus  der  analytischen  Praxis;  Bestimmung  von  Perchlorat 
in  Chilisalpeter :  Chem.  Ztg.,  Jahrg.  22,  1898,  p.  357. 


QUANTITATIVE   ANALYSIS.  65 

If  both  chloride  and  chlorate  are  present  in  addition  to  perchlorate, 
this  determination  gives  the  sum  of  all  three  of  these  ingredients 
weighed  as  silver  chloride.  A  separate  determination  of  chlorate 
by  one  of  the  methods  described  on  pages  62  and  63  gives  the  chlorate 
and  chloride  together  as  chlorides,  and  a  further  separate  deter- 
mination is  made  of  the  chloride  content  in  the  original  solution. 
From  these  results  the  amount  of  perchlorate  actually  present  is 
readily  calculated. 

NITRON    METHOD    FOB    DETERMINATION    OF    PERCHLOBATES. 

It  has  been  noted  (p.  61)  that  perchlorates  are  precipitated  by 
nitron,  and  therefore  interfere  with  the  determination  of  nitrates 
by  the  nitron  method  when  both  nitrates  and  perchlorates  are  con- 
tained in  the  same  solution.  The  extraordinarily  low  solubility  of 
nitron  perchlorate  (according  to  Busch,0  1:50,000)  suggested  the 
use  of  the  nitron  method  for  determining  perchlorates,  and  a  limited 
number  of  trials  has  justified  the  conclusion  that  perchlorates,  in 
the  absence  of  interfering  salts,  such  as  nitrates,  chlorates,  bromides, 
iodides,  chromates,  and  picrates,  may  be  accurately  determined  by 
precipitation  as  nitron  perchlorate. 

The  determinations  were  carried  out  by  exactly  the  same  method 
as  has  been  described  in  pages  60  to  62  for  determining  nitrates, 
about  0.12  gram  of  supposedly  pure  ammonium  perchlorate  being 
used  for  each  test.  The  weight  of  nitron  perchlorate  (C20H16N4. 
HC1O4)  found,  multiplied  by  the  molecular  weight  of  ammonium 
perchlorate  (117.5)  and  divided  by  the  molecular  weight  of  nitron 
perchlorate  (412.5),  is  equal  to  the  weight  of  ammonium  perchlorate. 
Two  determinations  showed  the  ammonium  perchlorate  to  have  a 
purity  of  99.67  and  99.58  per  cent,  respectively,  whereas  several 
determinations  by  the  fusion  method  (p.  64)  gave  a  purity  of  99.53 
per  cent. 

DETERMINATION  OF  NITRATES,  CHLORIDES,  CHLORATES,  AND  PERCHLORATES 

IN  A  MIXTURE. 

A  water  extract  containing  nitrates,  chlorides,  chlorates,  and  per- 
chlorates may  be  analyzed  by  proper  application  of  the  methods  de- 
scribed in  the  preceding  pages  of  this  bulletin. 

Chlorides  are  determined  gravimetrically  or  volumetrically  by 
precipitation  with  AgNO3.  Chlorates  are  determined  by  reduction 
with  SO2  gas  (see  p.  62)  or  formaldehyde  (see  p.  63)  and  precipita- 
tion of  the  resulting  chloride  with  AgNO3,  the  result  being  corrected 
for  the  chloride  originally  present  as  such. 

0  Busch,  M.,  Gravimetrische  Bestimmung  der  Salpetersaure :  Ber.  deut.  Chem.  Gesell., 
Jahrg.  38,  1905,  p.  861. 


66  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

Perchlorates  are  determined  by  fusing  with  Na2CO3  and  precipita- 
tion with  AgNO3  (see  p.  64),  the  total  chloride  thus  formed  being 
corrected  for  the  quantity  originally  present  plus  the  quantity  equiva- 
lent to  the  chlorate  originally  present.  Nitrates  are  determined  by 
reducing  the  chlorate  to  chloride  with  SO2  gas,  boiling  off  the  free 
SO2,  precipitating  the  combined  nitrate  and  perchlorate  with  nitron 
(see  pp.  60  and  65),  and  correcting  the  total  weight  of  nitron  nitrate 
and  nitron  perchlorate  for  the  weight  of  nitron  perchlorate  equiva- 
lent to  the  perchlorate  found  by  the  fusion  method. 

Obviously,  each  of  these  determinations  must  be  made  on  a  sepa- 
rate part  of  the  water  solution. 

DETERMINATION  OF  SOLUBLE  ORGANIC  MATERIALS  IN  THE  WATER  EXTRACT. 

In  addition  to  those  organic  substances  extracted  from  the  carbona- 
ceous combustible  material  which  have  been  mentioned,  such  soluble 
organic  substances  as  sugars  and  gums  may  be  contained  in  the 
water  extract  as  actual  constituents  of  the  explosive  mixture. 


DETERMINATION  OF  SUGARS. 


The  total  sugars  present  are  determined  as  follows:  An  aliquot 
part  of  the  water  extract  is  acidified  with  HC1  (1  c.  c.  of  strong  HC1 
to  100  c.  c.  of  solution),  heated  gradually  just  to  the  boiling  point 
in  order  to  invert  cane  sugar,  and  then  cooled.  The  acidity  is  nearly 
neutralized  with  Na2C03,  an  excess  of  Fehling's  solution  added,  and 
the  mixture  heated  on  the  steam  bath  until  reduction  is  complete. 
An  excess  of  Fehling's  solution  is  indicated  by  the  blue  oolor  of  the 
supernatant  liquid  after  the  precipitate  has  settled.  The  precipi- 
tated Cu2O  is  filtered  off  in  a  Gooch  crucible,  dried,  ignited  to  con- 
stant weight,  and  weighed  as  CuO,  or  merely  dried  and  weighed 
as  Cu2O. 

A  blank  determination  is  made  by  heating  an  equal  volume  of 
Fehling's  solution  as  in  the  determination  of  the  sugar,  filtering  off 
any  separated  Cu2O,  igniting  to  .CuO,  and  weighing.  This  weight 
of  CuO  is  deducted  from  that  obtained  in  the  determination  of  the 
sugar.  The  weight  of  CuO  multiplied  by  the  factor  0.4308  equals 
the  weight  of  cane  sugar,  and  the  corresponding  factor  for  Cu2O  is 
0.4790." 

In  order  to  determine  the  amount  of  sugar  in  the  water  extract  which 
might  result  from  cereal  products  in  the  explosive,  samples  of  corn 
meal,  wheat  flour  (middlings),  and  wood  pulp  were  extracted,  first 
with  ether  to  remove  oils,  then  with  cold  water,  and  the  total  sugars  in 
the  water  extracts  determined.  The  amounts  of  sugars  found  were : 
In  corn  meal  2.65  per  cent,  in  wheat  middlings  6.25  to  7  per  cent,  in 
wood  pulp  0.17  to.  0.62  per  cent.  Thus  if  an  explosive  contained  25 


0  Allen,  A.  H.,  Commercial  organic  analysis,  vol.   1,   1905,  p.  284. 


QUANTITATIVE   ANALYSIS.  67 

per  cent  of  wheat  middlings,  its  water  extract  might  show  a  sugar 
content  of  as  much  as  1.75  per  cent,  derived  from  extraction  of  the 
middlings  and  not  present  as  an  actual  constituent  of  the  explosive. 

DETEBMiNATION    OF    GUM    ARABIC. 

Gum  arabic  is  used  in  certain  granular  explosives  as  a  binding 
material  for  the  purpose  of  agglomerating  the  various  constituents 
of  the  explosive  into  more  or  less  regular  granules.  The  gum  arabic, 
being  entirely  soluble  in  water,  is  found  in  the  water  extract  and  may 
be  determined  with  approximate  accuracy  by  precipitation  with  basic 
lead  acetate.  The  precipitate  formed  is  white,  flocculent,  and  bulky. 

Because  of  the  fact  that  its  composition  is  not  definite,  it  is  neces- 
sary to  make  use  of  a  factor  obtained  from  the  results  of  precipitat- 
ing a  known  weight  of  gum  arabic  from  its  water  solution  by  the 
method  employed  in  making  the  determination  on  an  unknown 
solution. 

The  following  method  of  procedure  has  been  found  to  give  satis- 
factory results  : 

A  solution  of  basic  lead  acetate  is  prepared  by  adding  150  grams  of 
normal  lead  acetate  and  50  grams  of  lead  oxide  (PbO)  to  500  c.  c. 
of  distilled  water,  heating  the  mixture  almost  to  boiling,  and  filter- 
ing. Then  0.10  gram  of  powdered  gum  arabic  is  dissolved  in  cold 
water  and  basic  lead  acetate  solution  is  added  with  stirring  until  no 
further  precipitation  results;  the  mixture  is  then  allowed  to  stand 
for  several  hours,  the  precipitate  filtered  into  a  weighed  Gooch  cruci- 
ble, washed  several  times  with  absolute  alcohol,  dried  at  100°  C.,  and 
weighed.  Several  determinations  gave  an  average  of  0.2012  gram 
of  the  precipitate  from  0.10  gram  of  gum  arabic.  The  factor  for 
calculating  the  weight  of  gum  arabic  from  the  weight  of  the  pre- 

cipitate is  therefore  =0.4971. 


The  determination  of  the  gum  arabic  in  a  solution  is  carried  out 
in  exactly  the  above  manner.  The  weight  of  precipitate  multiplied  by 
the  factor  0.4971  gives  the  weight  of  the  gum  arabic  content. 

Most  of  the  usual  water-soluble  constituents  of  explosives  do  not 
interfere  with  the  determination  of  gum  arabic.  Any  chlorides  must, 
however,  be  removed  by  precipitation  with  silver  nitrate,  as  the  pre- 
cipitation of  lead  chloride  in  the  cold  solution  would  cause  high 
results. 

EXTRACTION   WITH    DILUTE    HYDROCHLORIC   ACID. 

The  principal  substances  soluble  in  cold  dilute  hydrochloric  acid 
are  the  antacids  added  to  the  explosive  to  neutralize  any  acidity  that 
may  be  present  or  might  later  develop  in  some  constituent  of  the 


68  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

explosive.  The  antacids  generally  used  are  calcium  or  magnesium 
carbonates  or  zinc  oxide ;  the  zinc  oxide  is  usually  found  in  the  water 
solution  if  the  explosive  contains  NH4NO3.  Other  substances,  more 
or  less  soluble  in  dilute  hydrochloric  acid,  that  may  form  part  of  the 
explosive  are  metallic  zinc,  aluminum,  manganese  dioxide,  and  ferric 
oxide.  A  sample  of  a  commercial  explosive,  recently  examined  in 
the  bureau's  laboratory,  contained  calcium  silicide. 

Extraction  with  cold  dilute  hydrochloric  acid  is  resorted  to  only 
when  the  explosive  contains  no  starch.  When  the  explosive  con- 
tains cereal  products  this  cold  acid  treatment  is  dispensed  with  and 
the  acid-soluble  inorganic  substances  are  removed  with  the  starch 
in  one  operation  by  hydrolysis  with  boiling  dilute  acid. 

EXTRACTION  WITH  COLD  DILUTE  ACID. 

The  extraction  with  cold  acid  is  carried  out  in  the  same  manner  as 
the  water  extraction,  using  the  suction  flask  fitted  with  rubber  stop- 
per and  carbon  tube,  Spencer  funnel,  or  other  device  for  holding  the 
filtering  crucible.  The  crucibles  containing  the  dried  and  weighed 
residues  left  after  extraction  with  water  are  placed  in  the  carbon 
tubes  or  other*  holders,  and  dilute  hydrochloric  acid  (1:10)  added. 
After  standing  for  a  short  time  this  acid  is  drawn  through  into  the 
flask  by  means  of  suction,  and-  a  fresh  portion  of  the  acid  added. 
This  treatment  is  continued  until  100  c.  c.  of  the  1 : 10  acid  has  passed 
through  the  sample  in  each  crucible.  The  excess  of  acid  is  then  re- 
moved from  the  samples  with  several  washings  of  water,  and  the 
crucibles  containing  the  insoluble  residue  dried  as  before  for  at  least 
5  hours  at  95°  to*  100°  C.  and  weighed  at  once  after  cooling  in  a 
desiccator. 

HYDROLYSIS  WITH  BOILING  DILUTE  HYDROCHLORIC  ACID. 

If  the  explosive  contains  starch*  the  extraction  with  cold  acid  is 
usually  omitted  and  the  hydrolysis  of  the  starch  carried  out  as 
follows : 

The  water-insoluble  residues  in  the  crucibles  are  moistened  with 
a  little  water  and  completely  transferred  by  means  of  a  spatula,  or 
with  a  stream  of  water  from  a  wash  bottle,  to  500  c.  c.  beakers.  If 
Gooch  crucibles  are  used,  the  asbestos  mats  are  removed  together  with 
the  residues  and  the  crucibles  are  dried  and  weighed.  The  weight 
of  asbestos  thus  determined  by  difference  from  the  original  weights 
of  the  prepared  crucibles  is  deducted  from  the  final  weight  of  dry 
residue  remaining  after  hydrolysis.  Water  is  added  to  the  beakers 
until  the  total  volume  is  about  300  c.  c.,  then  about  3  c.  c.  of  strong 
hydrochloric  acid  (specific  gravity  1.2)  is  added  and  the  mixture 


QUANTITATIVE   ANALYSIS. 


69 


boiled  until  the  starch  is  completely  hydrolyzed,  a  drop  of  the  solu- 
tion being  tested  from  time  to  time  on  a  spot  plate  with  a  solution 
of  iodine  in  potassium  iodide  until  a  blue  coloration  no  longer 
appears. 

The  insoluble  residue  is  then  filtered  onto  a  fresh  Gooch  crucible 
or  through  the  original  porous  crucible,  if  such  was  used,  washed 
with  water  to  remove  all  free  acid  and  dissolved  material,  dried  as 
before,  and  weighed,  the  weight  being  corrected  for  the  weight  of 
the  asbestos  mat  from  the  original  crucible. 

In  addition  to  hydrolyzing  the  starch  to  soluble  dextrine  and  dis- 
solving the  antacid  present,  the  boiling  with  dilute  acid  removes 
certain  soluble  parts  of  the  wood  pulp,  and  it  is  therefore  necessary 
that  the  boiling  should  be  continued  only  long  enough  completely 
to  hydrolyze  the  starch,  and  also  that  the  strength  of  the  acid  should 
be  no  greater  than  that  indicated  (approximately  1 : 100).  The  effect 
of  the  use  of  stronger  acid  is  shown  in  the  following  experiments  on 
three  samples  of  wood  pulp : 

SOLUBILITY  OF  WOOD  PULP  IN  BOILING  HYDROCHLORIC  ACID  OF  VARYING 

DILUTION. 

The  samples  of  wood  pulp  were  extracted  with  ether,  dried,  then 
extracted  with  cold  water,  and  again  dried.  Two-gram  parts  of  the 
extracted,  dried  samples  of  wood  pulp  were  then  boiled  for  15  minutes 
each  with  250  c.  c.  of  water  to  which  strong  hydrochloric  acid  in 
quantities  varying  from  2.5  to  25  c.  c.  had  been  added.  The  residues 
were  then  filtered,  washed,  dried,  and  weighed.  For  comparison 
another  2-gram  part  of  each  dried  sample  was  extracted  with  250  c.  c. 
of  cold,  dilute  acid  (1:10),  washed,  dried,  and  weighed. 

Loss  of  ivood  pulp  in  weight  on  boiling  with  hydrochloric  add  of  different 

concentrations. 


Volume  of 
water  used. 

Volume  of 
acid  added. 

Loss  fh  weight. 

Sample  157. 

Sample  158. 

Sample  175. 

C.c. 
250 
250 
250 
250 
250 

C.c. 
2.5 
5.0 
10.0 
20.0 
25.0 

Per  cent. 
11.71 
14.44 
18.10 
21.17 
22.63 

Per  cent. 
10.35 
13.25 
17.95 
23.95 
23.21 

Per  cent. 
12.55 
15.35 
19.35 
22.92 
25.91 

By  extraction  with  250  c.  c.  of  cold  acid  (1:10)  sample  157  lost 
3.60  per  cent,  sample  158  lost  3.97  per  cent,  and  sample  175  lost  4.10 
per  cent,  respectively. 

It  was  observed  that  as  the  concentration  of  the  acid  was  increased 
the  solubility  of  the  wood-pulp  samples  increased.  Even  with  1  part 


70  ANALYSIS  OF   PERMISSIBLE  EXPLOSIVES. 

acid  to  100  parts  water,  over  10  per  cent  of  the  original  dry  weight 
of  wood  pulp  was  dissolved  by  boiling. 

EXAMINATION  OF  ACID  SOLUTION. 

The  inorganic  substances  dissolved  by  either  the  extraction  with 
cold  hydrochloric  acid  (1:10)  or  boiling  with  dilute  hydrochloric 
acid  (1:100)  are  determined  in  the  filtrates  from,  the  insoluble 
residue  by  the  usual  methods. 

DETERMINATION   OF   ALUMINUM   AND   IRON. 

Both  aluminum  and  iron  may  be  present  in  small  proportions  as 
impurities  or  in  larger  proportions  if  metallic  aluminum  powder  or 
ferric  oxide  were  used  as  actual  ingredients  of  the  original  explosive. 

If  there  are  no  metals  other  than  Al,  Fe,  Ca,  and  Mg  in  the  acid 
solution,  the  entire  solution  may  be  used  for  the  successive  determina- 
tion of  these  substances  but  it  is  generally  advisable  to  use  only  one- 
half,  reserving  the  other  half. 

The  acid  solution  is  made  slightly  alkaline  with  NH4OH  and 
boiled  for  several  minutes.  If  the  precipitate  of  iron  or  aluminum 
hydroxides  is  very  small,  it  may  be  disregarded  and  the  calcium 
precipitated  without  previous  filtration,  otherwise  the  solution  is 
filtered  and  the  precipitate  dried  at  100°  C.,  ignited,  and  weighed 
as  Fe2O3  or  A12O3.  If  qualitative  tests  have  been  obtained  for  both 
iron  and  aluminum,  the  ignited  oxides  may  be  fused  with  potassium 
bisulphate,  the  fused  mass  dissolved  in  dilute  H2SO4,  the  dissolved 
iron  reduced  to  the  ferrous  condition  by  passing  H2S  through  the 
boiling  solution,  the  free  H2S  displaced  from  the  solution  by  a  cur- 
rent of  CO2,  and  the  iron  determined  by  titration  with  standard 
potassium  permanganate  solution.0 

DETERMINATION    OF    CALCIUM. 

The  filtrate  from  the  determination  of  iron  and  aluminum  is  used 
for  the  determination  of  calcium.  More  NH4OH  is  added  if  the 
solution  is  not  already  strongly  ammoniacal,  the  liquid  heated  to 
boiling,  hot  ammonium  oxalate  solution  added  in  slight  excess,  and 
the  boiling  continued  for  several  minutes.  The  precipitate  is  allowed 
to  settle  completely  and  then  is  filtered,  washed,  ignited,  and 
weighed  as  CaO. 

DETERMINATION    OF    MAGNESIUM. 

Magnesium  is  determined  in  the  filtrate  from  the  calcium  deter- 
mination by  evaporating  to  about  100  c.  c.,  adding  an  excess  of  a 
solution  of  sodium  hydrogen  phosphate  to  the  hot  solution,  then  a 

«Treadwell,  F.  P.,  Analytical  chemistry,  vol.  2,  1910,  p.  103. 


QUANTITATIVE   ANALYSIS.  71 

large  excess  of  NH4OH,  and  allowing  the  precipitate  to  settle  for 
several  hours.  The  precipitate  is  filtered,  washed,  ignited,  and 
weighed  as  Mg2P2O7. 

DETERMINATION    OF    ZINC. 

Any  zinc  which  may  be  contained  in  the  acid  solution  IB  deter- 
mined in  a  separate  aliquot  part  of  the  solution  by  precipitation  with 
Na2CO3,  as  described  on  page  58. 

DETERMINATION  OF  MANGANESE  DIOXIDE. 

Manganese  dioxide,  if  the  explosive  contains  it,  will  be  only  partly 
dissolved  by  extraction  with  cold  dilute  HC1  (1:10)  or  by  boiling 
with  dilute  HC1  (1 : 100)  to  hydrolyze  the  starch. 

The  manganese  dissolved  in  the  acid  solution  is  determined  by 
concentrating  a  part  of  the  solution  and  oxidizing  to  Mn3O4  by  means 
of  HNO3  and  KC1O3  crystals.  The  precipitated  Mn3O4  is  filtered 
off,  ignited,  and  weighed.  That  part  of  the  MnO2  in  the  insoluble 
residue  from  the  extraction  with  acid  is  determined  by  igniting  to 
drive  off  the  organic  material,  leaving  the  manganese  in  the  form  of 
Mn3O4,  which  is  weighed  direct. 

A  mixture  of  metallic  zinc,  manganese  dioxide,  and  flour  left  after 
extraction  with  water  was  analyzed  as  follows:  The  mixture  was 
transferred  from  the  crucible  to  a  beaker,  treated  with  boiling  dilute 
HC1  (1:100)  to  hydrolyze  the  starch  and  dissolve  the  metallic  zinc, 
a  part  of  the  MnO2  also  being  dissolved.  The  residue  was  ignited 
and  weighed  as  Mn3O4.  The  filtrate  was  evaporated  to  dryness  with 
H2SO4  and  ignited  to  convert  the  dissolved  zinc  and  manganese  to 
sulphates.  These  ignited  sulphates  were  dissolved  in  a  little  water, 
and,  without  filtering  off  the  small  quantity  of  Mn3O4  resulting  from 
decomposition  of  the  MnSO4,  the  solution  was  treated  with  an  excess 
of  strong  HNO3  and  evaporated  on  the  steam  bath,  with  the  frequent 
addition  of  crystals  of  potassium  chlorate.  The  residue  obtained  by 
evaporation  to  complete  dryness  was  redissolved  in  water,  the 
MnsO4  resulting  from  oxidation  of  the  MnSO4  was  filtered,  washed, 
ignited,  and  weighed.  The  zinc  in  the  filtrate  was  determined  by 
precipitation  with  Na2CO3  and  ignition  of  the  resulting  ZnCO3  to 
ZnO  (seep.  58). 

The  total  MnO2  originally  present  was  calculated  from  the  com- 
bined weights  of  Mn3O4  obtained  from  the  insoluble  part  and  the 
acid  solution. 

DETERMINATION  OF   CALCIUM   SILICIDE. 

Although  calcium  silicide  is  a  rather  unusual  ingredient  of  ex- 
plosives, the  fact  that  it  is  contained  in  at  least  one  commercial 


72  ANALYSIS  OF  PERMISSIBLE   EXPLOSIVES. 

blasting  explosive  used  in  this  country  justifies  a  brief  statement 
regarding  its  properties. 

Calcium  silicide  (CaSi2)  is  of  value  in  explosive  mixtures  for  the 
reason  that  its  oxidation  to  CaO  and  SiO2  produces  a  large  amount  of 
heat.  It  is  a  solid  substance  of  lead-gray  color,  metallic  luster,  and 
scaly  crystalline  structure.  On  treatment  with  dilute  hydrochloric 
acid  it  evolves  a  mixture  of  hydrogen  and  silicon  hydride  (SiH4), 
the  latter  being  spontaneously  inflammable.  This  behavior  serves 
as  an  excellent  means  of  identifying  calcium  silicide. 

The  solution  in  hydrochloric  acid  may  be  used  to  determine  the 
calcium,  from  which  the  amount  of  CaSi2  may  be  calculated. 

EXTRACTION   WITH    CARBON   BISULPHIDE. 

DETERMINATION-  OF  SULPHITE,. 

Extraction  with  carbon  bisulphide  is  necessary  only  when  the 
explosive  contains  a  large  proportion  of  sulphur.  The  extraction 
with  ether  for  the  usual  length  of  time  will  remove  all  of  the  sulphur 
if  the  amount  is  only  a  few  per  cent,  but  in  case  any  considerable 
quantity  of  sulphur  crystallizes  out  in  the  ether  solution,  it  is  ad- 
visable to  extract  with  carbon  bisulphide  to  insure  complete  removal 
of  this  constituent.  The  extraction  is  usually  made  on  the  dried  and 
weighed  residue  remaining  after  extraction  or  boiling  with  dilute 
hydrochloric  acid,  and  is  carried  out  in  the  Wiley  extraction  ap- 
paratus in  the  same  manner  as  the  extraction  with  ether.  After  ex- 
traction with  carbon  bisulphide  the  excess  solvent  remaining  in  the 
crucibles  is  removed  by  suction,  the  crucibles  left  in  a  warm  place 
until  the  odor  of  carbon  bisulphide  is  no  longer  noted,  and  then 
placed  in  an  oven  at  95°  to  100°  C.  to  dry  for  5  hours.  Attention  is 
called  to  the  fact  that  the  vapors  of  carbon  bisulphide  ignite  at 
temperatures  far  below  a  red  heat,  hence  there  is  danger  in  placing 
the  crucibles  wet  with  the  solvent  in  the  drying  oven  immediately 
after  extraction. 

The  loss  of  weight  of  the  residue  is  regarded  as  sulphur,  or,  in 
case  freshly  distilled  carbon  bisulphide  has  been  used  for  the  ex- 
traction, the  extract  may  be  evaporated  in  the  bell- jar  evaporator 
and  the  sulphur  weighed  direct.  The  weight  of  sulphur  found  by 
this  extraction  is  added  to  that  found  in  the  ether  extract. 

EXTRACTION   WITH   ACETONE. 

DETERMINATION  OF  NITROCELLULOSE  AND  NITROSTARCH. 

Extraction  with  acetone  is  necessary  only  when  the  qualitative 
examination  has  indicated  that  the  explosive  contains  nitrocellulose 
or  nitrostarch. 


QUANTITATIVE  ANALYSIS.  73 

Because  of  the  fact  that  nitrocellulose  is  used  in  some  explosives  in 
very  small  amounts,  its  presence  may  readily  be  overlooked,  espe- 
cially if  the  explosive  is  not  noticeably  gelatinous  in  its  consistency. 

Both  nitrocellulose  and  nitrostarch,  being  insoluble  in  ether,  water, 
carbon  bisulphide,  and  dilute  hydrochloric  acid,  may  be  determined 
after  all  of  these  extractions  have  been  made.  It  is  important  to 
note,  however,  that  these  organic  nitrates  are  gradually  decomposed 
by  long-continued  heating  at  temperatures  as  high  as  100°  C.,  and 
it  is  therefore  advisable,  when  either  nitrocellulose  or  nitrostarch 
have  been  found,  that  most  of  the  drying,  after  the  extractions  with 
ether,  water,  etc.,  be  done  at  a  temperature  of  70°  C.,  with  an  addi- 
tional half  hour  at  100°  C.  to  insure  constant  weight. 

METHOD   OF  TREATMENT   WITH   ACETONE. 

The  best  method  of  dissolving  nitrocellulose  or  nitrostarch  by 
means  of  acetone  is  as  follows:  The  residue  is  transferred  from  the 
crucible  to  a  100  c.  c.  beaker,  the  mat  being  left  in  the  crucible  if 
possible;  the  beaker  is  nearly  filled  with  acetone,  and  the  mixture 
permitted  to  stand  for  several  hours  with  frequent  stirring  in  order 
to  insure  complete  solution.  When  gelatinous-like  "flocks"  no 
longer  show  in  the  solutiori,  it  is  filtered  through  the  original  cru- 
cible, and  the  residue  washed  thoroughly  with  acetone.  If  the 
sample  contains  a  large  quantity  of  nitrostarch,  as  do  some  of  the 
nitrostarch  explosives,  the  solution  may  filter  with  difficulty;  in 
that  case  the  beaker  should  be  allowed  to  stand  until  the  insoluble 
residue  has  completely  settled,  the  clear  solution  carefully  decanted, 
and  fresh  acetone  added  to  the  insoluble  residue  before  attempting 
to  filter.  In  this  manner  most  of  the  soluble  material  is  removed 
before  filtering,  and  the  filter  does  not  become  so  easily  clogged. 

The  residue  left  in  the  filter  after  thorough  washing  with  acetone 
is  dried  and  weighed  as  usual,  and  the  loss  of  weight  regarded  as 
nitrocellulose  or  nitrostarch,  as  the  case  may  be.  Which  of  these 
substances  the  explosive  contains  must  be  determined  by  microscopic 
examination  as  noted  under  "  Qualitative  Examination  "  (p.  15). 

RECOVERY  OF  NITROCELLULOSE  OR  NITROSTARCH  FROM  ACETONE  SOLUTION. 

The  organic  nitrate  dissolved  in  the  acetone  may  be  recovered  by 
the  following  method:  The  acetone  solution  is  slowly  added,  with 
continual  stirring,  to  about  twice  its  volume  of  water  heated  to  70° 
to  80°  C.,  the  mixture  heated  on  the  steam  bath  until  all  of  the  ace- 
tone has  been  evaporated,  and  the  precipitated  organic  nitrate  fil- 
tered off. 

The  precipitate  may  be  dried  and  weighed,  its  weight  serving  as  a 
check  on  the  determination  of  loss  of  weight  on  extraction,  and  its 
nitrogen  content  determined  by  means  of  the  nitrometer. 


74  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

EXAMINATION    OF    THE   INSOLUBLE    RESIDUE. 

The  insoluble  residue  left  after  all  extractions  have  been  com- 
pleted may  contain  any  of  the  substances  noted  in  the  list  of  com- 
ponents on  page  13.  All  of  these  substances  have  been  found  in 
permissible  explosives  tested  by  the  bureau,  and  there  are  other  ones 
possible  which  might  be  added  to  the  list. 

MICROSCOPIC   EXAMINATION. 

Absolute  identification  of  the  substances  contained  in  the  insoluble 
residue  from  the  last  extraction  is  frequently  difficult  and  often  is 
made  possible  only  by  means  of  a  careful  microscopic  examina- 
tion. Familiarity  with  the  appearance  of  such  materials  under  the 
microscope  is  therefore  of  great  assistance. 

Two  types  of  microscopes  have  been  found  useful  in  the  bureau's 
laboratory — a  binocular  microscope,  by  means  of  which  magnifica- 
tions from  about  10  to  75  diameters  may  be  obtained,  and  an  ordinary 
petrographic  microscope  which  gives  magnifications  ranging  from 
about  20  to  300  diameters.  The  former  type  is  the  more  valuable 
for  the  examination  of  coarse  materials,  because  of  the  great  depth 
of  focus  obtainable,  whereas  the  petrographic  microscope,  with  its 
higher  powers  of  magnification,  is  useful  for  the  identification  of 
finer  materials. 

PREPARATION    OF    SLIDES. 

Careful  mounting  of  the  samples  for  microscopic  examination  is 
not  at  all  necessary.  The  usual  method  is  to  spread  a  small  quantity 
of  the  dry  residue  uniformly  over  the  surface  of  the  glass  micro- 
scope slide  in  a  thin  layer  so  that  individual  particles  are  separated 
from  each  other,  placing  the  slide  directly  under  the  objective,  with- 
out a  cover  glass. 

The  most  suitable  magnification  to  use  is  determined  by  trial.  A 
number  of  samples  of  different  materials  that  may  be  found  in  the 
insoluble  residue  are  shown  in  Plates  I,  II,  and  III  under  magnifi- 
cations of  10  to  150  diameters. 

In  Plate  I,  A  and  B,  is  shown  wood  pulp  of  different  grades; 
Plate  I,  (7,  shows  fine  sawdust  with  its  characteristic  bundles  of 
fibers ;  in  Plate  I,  D  and  E,  different  types  of  kieselguhr  or  infusorial 
earth  are  illustrated;  and  Plate  I,  F,  shows  the  crude  fiber  from 
coarse  wheat  flour  (middlings)  left  after  hydrolysis  of  the  starch. 

A  and  B,  Plate  II,  represent  cotton  (cellulose)  and  nitrocellulose, 
respectively,  both  of  which  appear  alike  under  the  microscope  unless 
examined  in  polarized  light,  when  the  unnitrated  fibers  appear  in 
brilliant  colors  and  the  nitrated  fibers  are  dark;  Plate  II,  (7,  repre- 


BUREAU    OF   MINES 


BULLETIN    96       PLATE 


A.     WOOD  PULP  NO.  1    (X  50). 


E.     INFUSORIAL  EARTH  NO.  2   (X   150). 


B.     WOOD  PULP  NO.  2  (X  50). 


o 


\ 


0 


D.     INFUSORIAL  EARTH  NO.   1    (X   150). 


t  ^     "  '      ' 

. 


.  -  ' 


% 

;jl 

•>;  m 

'•"^ " 


.F.     CRUDE  FIBER  FROM  WHEAT  MID- 
DLINGS (X  25). 


QUANTITATIVE   ANALYSIS.  75 

sents  fine  wheat  flour ;  Plate  II,  Z>,  fine  wheat  flour  mixed  with  wood 
pulp ;  Plate  II,  /?,  coarse  wheat  flour  (middlings) ;  and  Plate  II,  F, 
fine  corn  meal. 

A  number  of  the  more  unusual  carbonaceous  combustible  materials 
used  in  explosives  are  illustrated  in  Plate  III.  In  this  plate  A 
shows  peanut-shell  meal;  B,  rice  hulls;  (7,  corncob  meal  (com- 
mercially known  as  "Corona  meal");  and  Z>,  "vegetable  ivory" 
meal,  a  product  obtained  by  pulverizing  the  waste  resulting  in  the 
manufacture  of  buttons  from  "vegetable  ivory"  nuts  ("corosos" 
nuts) ,  the  fruit  of  the  phytelephas  macrocarpa  or  "  ivory  nut "  tree 
of  tropical  countries.  The  materials  shown  in  Plate  III  h.ave  prac- 
tically no  absorbent  properties,  their  chief  use  in  explosives  being 
to  serve  as  combustible  materials. 

DETERMINATION  OF  ASH. 

The  determination  of  "  ash  "  in  an  explosive,  that  is,  natural  inor- 
ganic insoluble  constituents  of  the  carbonaceous  materials,  plus  any 
insoluble  nonvolatile  impurities  in  the  various  salts  is,  of  course, 
possible  only  when  no  inorganic  substances  are  actual  constituents  of 
the  insoluble  residue.  The  amount  of  such  inorganic  materials  may 
be  determined,  however,  by  burning  off  the  organic  matter,  as  in  the 
determination  of  ash,  and  weighing  the  resulting  nonvolatile  residue, 
which  includes  the  ash. 

One  of  the  duplicate  samples  of  the  dried  and  weighed  insoluble 
residue  is  used  for  the  determination  of  ash,  or  of  combined  ash 
and  inorganic  substances.  This  residue  may  be  ignited  in  the  origi- 
nal filtering  crucible  in  which  it  was  dried,  the  organic  material 
being  burned  by  first  heating  it  very  gradually  with  a  small  free 
flame  of  a  burner  until  combustible  gases  cease  to  be  evolved,  then 
increasing  the  size  of  the  flame  and  tilting  the  crucible  so  that  the 
carbon  is  finally  burned  off,  leaving  a  constant  weight  of  inorganic 
residue. 

If  desired,  the  ignition  may  be  carried  out  in  a  platinum  crucible 
by  transferring  to  it  all  the  dried  and  weighed  residue  from  the 
original  filtering  crucible.  This  method  involves  an  additional 
weighing  (of  the  platinum  crucible)  but  the  combustion  is  more 
rapid  .in  the  platinum  crucible  than  in  the  porcelain  or  alundum 
filtering  crucibles. 

The  proportion  of  ash  is  usually  not  over  0.20  per  cent.  If  it  is 
over  0.5  per  cent,  the  residue  probably  contains,  in  addition  to  the  real 
ash  of  the  carbonaceous  materials,  insoluble  inorganic  impurities 
from  some  of  the  saline  ingredients,  or  possibly  small  amounts  of 
added  inorganic  material,  such  as  kieselguhr,  clay,  etc.  A  high  ash 
content  may  also  indicate  that  either  the  water  or  acid  extractions 


76 


ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 


have  not  been  complete.     In  this  respect  the  determination  of  ash 
may  be  regarded  as  a  check  on  the  analysis. 

THE   ULTIMATE   COMPOSITION  OF  CARBONACEOUS  IN.GBEDIENTS. 

In  making  calculations  of  the  reactions  involved  in  the  explosive 
decomposition  of  explosive  mixtures  for  the  purpose  of  calculating 
the  temperatures,  gas  volumes,  etc.,  resulting  from  explosion,  it  was 
essential  that  the  average  ultimate  composition  of  the  various  car- 
bonaceous ingredients  be  known  so  that  the  formulas  used  to  repre- 
sent the  composition  of  these  substances  might  be  as  nearly  correct 
as  possible. 

ULTIMATE  COMPOSITION  OF  WOOD  PULP. 

The  results  of  analyses  of  different  woods  by  various  investigators 
were  collected  and  averaged.  A  summary  of  these  results  is  shown 
in  the  following  table : 

Results  of  analyses  of  woods  by  different  investigators. 
[Average  ultimate  composition.] 


Designation 
of  test. 

Proportion  of— 

Authority. 

Remarks. 

Carbon. 

Hydro- 
gen. 

Oxygen.o 

A.. 

Per  cent. 
49.77 
49.50 
50.64 
50.00 
49.20 
50.00 

Per  cent. 
6.15 
6.00 
6.17 
6.00 
6.10 
6.00 

Per  cent. 
44.08 
44.50 
43.19 
44.00 
44.70 
44.00 

Gottlieb  6  
Poole  c  

Average  of  7  kinds  of  wood. 
Average  of  5  kinds  of  wood. 
Average  of  13  kinds  of  wood. 

B      

c 

Chevandier  d  .  . 
Aufhauser  «... 
Chevandier/.. 
Mucks'  

D 

E 

F       .  .  

Average  

49.85 

6.07 

44.08 

a  Includes  small  amount  of  nitrogen. 
&  Poole,  H.,  Calorific  value  of  fuels,  1905,  p.  86. 
c  Poole,  H.,  op.  cit.,  p.  85. 

d  Gody,  L.,  Traite"  theorique  et  pratique  des  matieres  explosives,  1907,  p.  67. 

«  Aufhauser,  — ,  Die  spezifischen  Eigenschaf ten  und  Unterschiede  der festenund  fliissigen  Brennstoffe  und 
ihre  technische  Bedeutung:  Gliickauf,  Jahrg.  49,  1913,  p.  604. 

/  Juptner,  H.  von,  Lehrbuch  der  chemischen  Technologic  der  Energien,  Bd.  1,  1905,  p.  154. 
g  Juptner,  H.  von,  op.  cit.,  p.  170. 

This  average  composition  corresponds  to  the  empirical  formula 
C15H21.9O9.9,  or  expressed  in  round  numbers,  C15H22O10,  which  .is  the 
formula  used  by  chemists  of  the  bureau  in  previous  works.0 

In  order  to  check  this  result,  by  tests  of  wood  pulp  actually  used 
in  the  manufacture  of  explosives  in  this  country,  samples  of  wood 
pulp  were  obtained  from  various  manufacturers  of  permissible  explo- 

0  Hall,  C.,  Snelling,  W.  O.,  and  Howell,  S.  P.,  Investigations  of  explosives  used  in  coal 
mines :  Bull.  15,  Bureau  of  Mines,  1912,  p.  62. 


BUREAU    OF    MINES 


BULLETIN    96      PLATE   II 


A.     CELLULOSE   (COTTON)   (X  50), 


B,     NITROCELLULOSE  (X  50). 


C.     WHEAT  FLOUR  (FINE)   (X  50). 


D.     WHEAT  FLOUR  (FINE)  AND  WOOD 
PULP  (X  50). 


E.     WHEAT  FLOUR   (MIDDLINGS)   (X  50). 


F.     CORN  MEAL  (X  50). 


QUANTITATIVE   ANALYSIS. 


77 


sives  and  submitted  to  careful  ultimate  analyses  by  the  combustion 
method,  with  the  following  results: 

Results  of  analyses  of  wood  pulp  used  in  explosives  in  the  United  States. 
[Analyses  made  undor  direction  of  A.  C.  Fieldner.] 


Designation  of  sample. 
(Lab.  No.) 

Composition  of  samples  "  as  received.  " 

Composition  of  samples  cal- 
culated free  from  ash  and 
moisture. 

Mois- 
ture. 

Ash. 

Carbon. 

Hydro- 
gen. 

Carbon. 

Hydro- 
gen. 

Oxygen 
(by  dif- 
ference). 

156         

Per  cent. 
9.33 
6.83 
6.53 
6.50 
7.35 
5  73 

Per  cent. 
0.59 
.70 
.23 
.24 
.32 
.38 
.48 
.46 
.82 

Per  cent. 
46.14 
47.20 
48.40 
47.53 
46.40 
48.19 
46.18 
47.40 
47.22 

Per  cent. 
6.68 
6.37 
6.50 
6.42 
6.45 
6.35 
6.41 
6.44 
6.30 

Per  cent. 
51.22 
51.04 
51.91 
50.99 
50.26 
51.32 
51.19 
51.03 
51.17 

Per  cent. 
6.25 
6.07 
6.18 
6.11 
6.10 
6.09 
5.96 
6.13 
5.99 

Per  cent. 
42.53 
42.89 
41.91 
42.90 
43.64 
42.59 
42.85 
42.84 
42.84 

157 

158         

159 

163       „  

165  

9.30 
6.63 
0.90 

166 

167  

Average  

51.12 

6.10 

42.78 

The  average  composition  of  the  nine  samples  of  wood  pulp — 
51.12  per  cent  carbon,  6.10  per  cent  hydrogen,  and  42.78  per  cent 
oxygen — does  not  differ  widely  from  the  average  of  the  results 
found  in  the  literature  (see  p.  76).  The  empirical  formula  cal- 
culated from  these  results  is  C15H21.5O9.5,  which,  like  the  formula 
on  page  76  may  also  be  expressed  as  C15H22O10. 

This  formula  for  wood  pulp  has  therefore  been  accepted  for  use 
in  calculations  based  upon  the  chemical  reactions  involved  in  the 
explosion  of  blasting  explosives  containing  this  ingredient. 

ULTIMATE   COMPOSITION  OF   CORN  MEAL. 

In  view  of  the  fact  that  no  results  of  ultimate  analyses  of  corn 
meal  could  be  found  in  the  literature  on  the  subject,  an  attempt  was 
made  to  calculate  such  an  analysis  from  the  results  of  average  proxi- 
mate analyses.  The  following  was  selected  as  an  average  proximate 
analysis  of  corn  meal:a 

Composition  of  corn  meal. 


Constituent. 

Proportion  in  corn 
meal. 

By  analy- 
sis. 

Calculated 
on  ash-free 
and  mois- 
ture-free 
basis. 

Moisture                                            

Per  cent. 
12.57 
7.13 
1.33 
.87 
78.36 
.61 

Per  cent. 

Proteids 

8.13 
1.52 
.99 
89.36 

Ether  extract 

Crude  fiber                                                                                  .              

Ash... 

0  Wiley,  H.  W.,  Composition  of  maize  (Indian  corn),  including  the  grain,  meal,  stalks, 
pith,  fodder,  and  cobs  :  Bureau  of  Chemistry,  Department  of  Agriculture,  Bull.  50,  1898, 
p.  13. 

10293°— Bull.  96—16 6 


78  ANALYSIS  OF   PERMISSIBLE   EXPLOSIVES. 

The  composition  of  the  proteid  was  assumed  to  be  as  follows: 
C,  55.22  per  cent;  H,  T.25  per  cent;  N,  16.15  per  cent;  S,  0.61  per 
cent;  O,  20.77  per  cent,  this  being  the  average  composition  of  the 
zeins  which  compose  the  proteids." 

The  composition  of  the  ether  extract  was  calculated  as  C,  75.16 
per  cent,  H,  11.72  per  cent,  and  O,  12.69  per  cent  from  the  average 
of  the  compositions  given  by  Konig &  and  Hopkins.0 

The  crude  fiber  was  assumed  to  have  the  same  formula  as  wood 
pulp,  C15H22O10,  or  approximately  49.72  per  cent  C,  6.08  per  cent  H, 
and  44.2  per  cent  O. 

The  carbohydrates  were  assumed  to  be  sugar  and  starch,  the  sugar 
constituting  1.75  per  cent  of  the  total  meal,5  or  2.22  per  cent  of  the 
moisture-free  and  ash-free  material. 

If  the  above  assumptions  are  accepted  and  the  small  proportion  of 
sulphur  in  the  proteids  be  disregarded,  the  ultimate  composition  of 
the  moisture-free  and  ash-free  material,  calculated  from  the  proxi- 
mate analysis,  is  as  follows:  C,  45.77  per  cent;  H,  6.35  per  cent;  O, 
46.51  per  cent;  N,  1.37  per  cent.  This  composition  gives  approxi- 
mately the  empirical  formula,  C^H^On^No^. 

The  average  of  three  analyses  of  corn  meal,  kindly  reported  to  the 
writer  by  Prof.  H.  P.  Ormsby,  of  Pennsylvania,  State  College,  is  as 
follows:  C,  46.46  per  cent;  H,  6.74  per  cent;  O,  45.06  per  cent;  N, 
1.74  per  cent.  The  formula  calculated  from  this  composition  is 
C15H26O10.9N0.5,  which  agrees  closely  with  the  formula  calculated 
from  the  proximate  analysis. 

Both  of  these  results  were  closely  confirmed  by  the  results  of  two 
analyses  of  corn  meal  by  A.  C.  Fieldner,  of  the  Bureau  of  Mines, 
which  averaged  46.87  per  cent  C,  6.50  per  cent  H,  45.43  per  cent  O, 
1.20  per  cent  1ST,  corresponding  to  the  formula  QnHj^Ou^s- 

The  average  of  the  three  formulas  obtained  as  above  noted  is 
dgH^Ou-iNo^,  which,  for  all  practical  purposes,  may  be  written 
C^HggOn.  It  is  believed  that  this  formula  approximates  the  aver- 
age composition  of  dry  corn  meal,  and  may  be  used  in  calculations 
where  a  formula  for  corn  meal  is  required. 

ULTIMATE  COMPOSITION  OF  WHEAT  FLOUR. 

The  ultimate  composition  of  wheat  flour,  or  middlings,  was  cal- 
culated, by  the  method  used  for  corn  meal,  from  an  average  of  a 
large  number  of  proximate  analyses.  The  calculated  composition 

0  Wiley,  H.  W.,  Composition  of  maize  (Indian  corn),  including  the  grain,  meal,  stalks, 
pith,  fodder,  and  cobs :  Bureau  of  Chemistry,  Department  of  Agriculture,  Bull.  50,  1898, 
p.  9. 

»  Blyth,  A.  W.,  and  Blyth,  M.  W.,  Foods,  their  composition  and  analysis,  1903,  p.  216. 

e  Benedikt-Ulzer,  Analyse  der  Fette  und  Wachsarten,  Auf.  5,  1908,  p.  715. 

d  Bryan,  A.  G.,  Given,  A.,  and  Straughn,  M.  N.,  Extraction  of  grains  and  cattle  foods 
for  the  determination  of  sugars ;  a  comparison  of  the  alcohol  and  the  sodium  digestions : 
Bureau  of  Chemistry,  Department  of  Agriculture,  Circular  71,  1911,  14  pp. 


BUREAU    OF    MINES 


BULLETIN    96      PLATE    III 


A.     PEANUT-SHELL  MEAL  (X   15). 


B.     RICE  HULLS  (X   15). 


C.     CORNCOB  MEAL  (X   15). 


D.     VEGETABLE-IVORY  MEAL  (X   15). 


QUANTITATIVE  ANALYSIS.  79 

was  46.65  per  cent  C,  6.43  per  cent  H,  44.10  per  cent  O,  2.67  per  cent 
N,  0.15  per  cent  S,  and  corresponds  to  the  formula  C15H.,4.8O10.6N0.7 
(the  sulphur  being  disregarded). 

Four  samples  of  wheat  middlings  analyzed  by  A.  C.  Fieldner  gave 
an  average  composition  of  46.46  per  cent  C,  6.44  per  cent  H,  44.61 
per  cent  O,  2.33  per  cent  N,  and  0.16  per  cent  S,  a  composition  that 
corresponds  to  the  formula  C15H25O10.8N0.6. 

Both  of  these  formulas  may,  like  those  for  corn  meal,  be  expressed 
as  CjgHogOn,  which  formula,  it  is  considered,  may;  be  used  in  explo- 
sives calculations  as  being  approximately  accurate  for  dry  wheat 
flour,  or  middlings. 

CONCLUDING  REMARKS. 

In  describing  the  methods  employed  by  the  Bureau  of  Mines  for 
the  analysis  of  explosives  submitted  for  tests,  it  has  been  impossible 
to  discuss  in  detail  the  methods  used  for  the  analysis  of  all  the 
various  combinations  of  ingredients  which  have  been  found  in  the 
many  different  explosives  examined,  or  which  may  be  met  with  in 
explosives  submitted  in  the  future.  It  has  frequently  been  necessary 
to  devise  methods  for  the  analysis  of  some  unusual  mixture  of  ingre- 
dients in  an  explosive. 

It  is  believed,  however,  that  the  methods  described  in  this  bulletin 
will  be  of  material  assistance  to  chemists  engaged  in  the  analysis  of 
the  various  types  of  blasting  explosives. 


APPENDIX. 

TOLERANCES  FOB  PERMISSIBLE  EXPLOSIVES. 

At  a  conference  on  June  7,  1915,  between  manufacturers  of  ex- 
plosives and  the  bureau's  engineers  and  chemists  an  agreement  was 
reached  providing  for  reasonable  limits  of  variation  or  "  tolerances  " 
in  the  results  of  analyses  and  tests  of  permissible  explosives.  If 
these  tolerances  are  exceeded  by  a  given  lot  of  any  permissible  ex- 
plosive it  is  not  permissible.  The  tolerances  established,  which  were 
made  effective  July  1,  1915,  are  stated  as  follows: 

In  order  to  define  more  exactly  what  is  meant  by  the  phrase  "similar  in  all  respects'^ 
in  the  definition  of  a  permissible  explosive,  namely,  "an  explosive  is  called  a  per- 
missible explosive  when  it  is  similar  in  all  respects  to  the  sample  that  passed  certain 


LIMIT  OF  VARIATION,  PERCENTAGE  OI 
TOTAL  EXPLOSIVE. 

0  J-  f»  JO  tO  CO  CO 

OCnOCnOOiOCn 

*** 

+>* 

—  ^ 

^^ 

^ 

!*••* 

^^ 

,**• 

^•* 

^ 

^ 

f* 

^ 

S 

^^ 

^ 

r 

• 

10         15 


20 


25         30         35 


40 


45         50         55         60 


05 


QUANTITY  OF  CONSTITUENT,  PER  CENT. 
FIGURE  7.— Curve  of  limit  variation  in  composition  of  permissible  explosives. 

tests  by  the  United  States  Bureau  of  Mines,  and  when  it  is  used  in  accordance  with 
the  conditions  prescribed  by  this  bureau,"  the  following  tolerances  are  recommended 
for  field  samples  or  manufacturers'  samples  of  explosives,  beyond  which  such  lot  of 
explosives  can  not  vary  and  still  be  considered  permissible  for  use  in  coal  mines: 
Provided,  That  where  the  Bureau  of  Mines  finds  a  sample  which  does  not  come  up 
to  the  tolerance  limits,  the  bureau  shall  simply  declare  that  particular  lot  of  explosives 
not  permissible,  and  a  copy  of  the  notification  to  the  consumer  or  owner  shall  be 
furnished  the  manufacturer,  the  notification  to  state  that  the  explosive  did  not  meet 
the  tolerance  requirements  for  moisture  or  ingredients,  etc.,  as  the  case  might  be. 

Chemical  analysis. — Moisture,  to  be  fixed  by  a  sliding  scale  of  from  ]£  per  cent  at 
zero  to  4  per  cent  at  10  per  cent  of  moisture  in  original  sample,  this  tolerance  being 
on  total  percentage  of  moisture  in  the  explosive. 

Other  ingredients  (or  their  equivalents)  in  quantities  not  exceeding  60  per  cent, 
according  to  a  curve  [shown  in  figure  7].  For  ingredients  in  quantities  of  60  per  cent 
80 


MINE   ACCIDENTS    A.ND   TESTS   OF   EXPLOSIVES.  81 

or  more,  the  tolerance  shall  be  plus  or  minus  3  per  cent:  Provided,  That  the  ingredients 
of  a  permissible  explosive  shall  be  considered  to  be  those  substances  reported  as 
found  by  the  Bureau  of  Mines  in  the  original  sample  of  that  explosive  submitted 
for  test  as  to  its  permissibility:  And  provided  furtJier,  That  an  equivalent  shall  be 
considered  to  be  a  substance  which  would  not  materially  alter  the  properties  of  the 
explosive  and  which  would  produce  the  same  result  as  the  original  substance. 

Products  of  combustion  (determined  by  Bichel  gage  test). — The  volume  of  poison- 
ous gases  from  680  grams  of  the  explosive,  including  its  wrapper,  must  be  less  than 
158  liters,  except  that  in  case  the  first  test  yields  158  liters  or  more  of  poisonous  gases 
per  680  grams  of  the  explosive,  including  its  wrapper,  the  average  result  of  three 
tests  agreeing  within  5  per  cent  of  each  other  shall  be  taken,  and  no  explosive  shall 
remain  permissible  when  this  average  for  poisonous  gases  exceeds  the  above  standard 
limit. 

Physical  tests. a— 

Rate  of  detonation  (the  average  of  three  trials  with  Mettegang's  recorder),  plus  or 
minus  15  per  cent. 

Unit  deflective  charge  (the  average  of  three  trials  with  the  ballistic  pendulum), 
plus  or  minus  10  per  cent. 

Grams  of  wrapper  per  100  grams  of  explosive,  plus  or  minus  2.0  grams  (average  of 
four  determinations):  Provided,  That  the  manufacturers  shall  submit  samples  of  all 
different  sizes  of  cartridges,  to  be  considered  as  part  of  the  original  sample,  the  amount 
of  wrapper  to  be  determined  for  each  size  of  sample:  And  provided  further,  That  the 
tolerances  as  suggested  shall  be  determined  in  comparison  with  the  various  diameters 
of  samples  as  submitted  with  the  original  sample. 

Apparent  specific  gravity  of  cartridge,  by  sand,  plus  or  minus  7.5  per  cent  (average 
of  four  determinations):  Provided,  that  actual  density  shall  be  determined  on  car- 
tridges of  the  same  diameter  as  the  standard:  And  provided  further,  That  manufacturers 
shall  be  required  to  submit  samples  of  all  sizes. 

Gas  and  dust  gallery  No.  1. — No  ignition  must  be  obtained  in  each  of  one  or  more 
trials.  Note:  In  the  retesting  of  permissible  explosives  by  tests  1,  3,  and  4,&  the 
charges  of  the  explosives  fired  will  be  reduced  10  per  cent  in  weight  from  the  weights 
originally  used  in  order  to  eliminate  any  likelihood  of  a  failure  being  due  to  the 
natural  variations  in  the  gallery  conditions. 

Pendulum  friction  test. — Each  explosive  must  pass  a  test  of  10  trials  under  the 
same  conditions  as  originally  tested,  except  that  the  height  of  fall  of  the  wood-fiber 
shoe  will  be  reduced  by  10  per  cent  in  order  to  eliminate  any  likelihood  of  a  failure 
being  due  to  the  natural  variations  in  test  conditions. 

a  For  methods  of  making  these  tests,  see  Hall, Clarence,  and  Howell,  S.  P.,  Tests  of  permissible  explosives: 
Bull.  66,  Bureau  ol  Mines,  1913, 313  pp. 
b  Op.  cit.,  p.  303. 


PUBLICATIONS  ON  MINE  ACCIDENTS  AND  TESTS  OF 

EXPLOSIVES. 

A  limited  supply  of  the  following  publications  of  the  Bureau  of 
Mines  is  temporarily  available  for  free  distribution.  Requests  for 
all  publications  can  not  be  granted,  and  applicants  should  select  only 
those  publications  that  are  of  especial  interest  to  them.  All  requests 
for  publications  should  be  addressed  to  the  Director,  Bureau  of 
Mines,  Washington,  D.  C. 

BULLETIN  15.  Investigations  of  explosives  used  in  coal  mines,  by  Clarence 
Hall,  W.  O.  Snelling,  and  S.  P.  Howell,  with  a  chapter  on  the  natural  gas  used 
at  Pittsburgh,  by  G.  A.  Burrell,  and  an  introduction  by  C.  E.  Munroe.  1912. 
197  pp.,  7  pis.,  5  figs. 

BULLETIN  17.  A  primer  on  explosives  for  coal  miners,  by  C.  E.  Munroe  and 
Clarence  Hall.  61  pp.,  10  pis.,  12  figs.  Reprint  of  United  States  Geological 
Survey  Bulletin  423. 

BULLETIN  20.  The  explosibility  of  coal  dust,  by  G.  S.  Rice,  with  chapters  by 
J.  C.  W.  Frazier,  Axel  Larsen,  Frank  Haas,  and  Carl  Scholz.  204  pp.,  14  pis., 
28  figs.  Reprint  of  United  States  Geological  Survey  Bulletin  425. 

BULLETIN  48.  The  selection  of  explosives  used  in  engineering  and  mining 
operations,  by  Clarence  Hall  and  S.  P.  Howell.  1913.  50  pp.,  3  pis.,  7  figs. 

BULLETIN  51.  The  analysis  of  black  powder  and  dynamite,  by  W.  O.  Snelling 
and  C.  G.  Storm.  1913.  80  pp.,  5  pis.,  5  figs. 

BULLETIN  56.  First  series  of  coal-dust  explosion  tests  in  the  experimental 
mine,  by  G.  S.  Rice,  L.  M.  Jones,  J.  K.  Clement,  and  W.  L.  Egy.  1913.  115  pp., 
12  pis.,  28  figs. 

BULLETIN  59.  Investigations  of  detonators  and  electric  detonators,  by  Clarence 
Hall  and  S.  P.  Howell.  1913.  73  pp.,  7  pis.,  5  figs. 

BULLETIN  66.  Tests  of  permissible  explosives,  by  Clarence  Hall  and  S.  P. 
Howell.  1913.  313  pp.,  1  pi.,  6  figs. 

BULLETIN  68.  Electric  switches  for  use  in  gaseous  mines,  by  H.  H.  Clark  and 
R.  W.  Crocker.  1913.  40  pp.,  6  pis. 

BULLETIN  69.  Coal-mine  accidents  in  the  United  States  and  foreign  countries, 
compiled  by  F.  W.  Horton.  1913.  102  pp.,  3  pis.,  40  figs. 

BULLETIN  72.  Occurrence  of  explosive  gases  in  coal  mines,  by  N.  H.  Darton. 
1915.  248  pp.,  7  pis.,  33  figs. 

BULLETIN  80.  A  primer  on  explosives  for  metal  miners  and  quarrymen,  by 
C.  E.  Munroe  and  Clarence  Hall.  1915.  122  pp.,  15  pis.,  7  figs. 

TECHNICAL  PAPER  6.  The  rate  of  burning  of  fuse  as  influenced  by  temperature 
and  pressure,  by  W.  O.  Snelling  and  W.  C.  Cope.  1912.  28  pp. 

TECHNICAL  PAPER  7.  Investigations  of  fuse  and  miners'  squibs,  by  Clarence 
Hall  and  S.  P.  Howell.  1912.  19  pp. 

TECHNICAL  PAPER  11.  The  use  of  mice  and  birds  for  detecting  carbon  monoxide 
after  mine  fires  and  explosions,  by  G.  A.  Burrell.  1912.  15  pp. 

82 


MINE  ACCIDENTS  AND  TESTS  OF  EXPLOSIVES.  83 

TECHNICAL  PAPEB  12.  The  behavior  of  nitroglycerin  when  heated,  by  W.  O. 
Snelling  and  C.  G.  Storm.  1912.  14  pp.,  1  pi.,  2  figs. 

TECHNICAL  PAPER  13.  Gas  analysis  as  an  aid  in  fighting  mine  fires,  by  G.  A. 
Burrell  and  F.  M.  Seibert.  1912.  16  pp.,  1  fig. 

TECHNICAL  PAPEB  17.  The  effect  of  stemming  on  the  efficiency  of  explosives, 
by  W.  O.  Snelling  and  Clarence  Hall.  1912.  20  pp.,  11  figs. 

TECHNICAL  PAPER  18.  Magazines  and  thaw  houses  for  explosives,  by  Clarence 
Hall  and  S.  P.  Howell.  1912.  34  pp.,  1  pi.,  5  figs. 

TECHNICAL  PAPER  21.  The  prevention  of  mine  explosions,  report  and  recom- 
mendations, by  Victor  Watteyne,  Carl  Meissner,  and  Arthur  Desborough.  12  pp. 
Reprint  of  United  States  Geological  Survey  Bulletin  369. 

TECHNICAL  PAPER  30.  Mine-accident  prevention  at  Lake  Superior  iron  mines, 
by  D.  E.  Woodbridge.  1913.  38  pp.,  9  figs. 

TECHNICAL  PAPER  39.  The  inflammable  gases  in  mine  air,  by  G.  A.  Burrell 
and  F.  M.  Seibert.  1913.  24  pp.,  2  figs. 

TECHNICAL  PAPER  44.  Safety  electric  switches  for  mines,  by  H.  H.  Clark. 
1913.  8  pp. 

TECHNICAL  PAPER  47.  Portable  electric  mine  lamps,  by  H.  H.  Clark.  1913. 
13  pp. 

TECHNICAL  PAPER  48.  Coal-mine  accidents  in  the  United  States,  1896-1912, 
with  monthly  statistics  for  1912,  compiled  by  F.  W.  Horton.  1913.  74  pp.,  10 


TECHNICAL  PAPER  61.  Metal-mine  accidents  in  the  United  States  during  the 
calendar  year  1912,  compiled  by  A.  H.  Fay.  1913.  76  pp.,  1  fig. 

TECHNICAL  PAPER  62.  Relative  effects  of  carbon  monoxide  on  small  animals, 
by  G.  A.  Burrell,  F.  M.  Seibert,  and  I.  W.  Robertson.  1914.  23  pp. 

TECHNICAL  PAPER  67.  Mine  signboards,  by  Edwin  Higgins  and  Edward  Steidle. 
1913.  15  pp.,  1  pi.,  4  figs. 

TECHNICAL  PAPER  71.  Permissible  explosives  tested  prior  to  January  1,  1914, 
by  Clarence  Hall.  1914.  12  pp. 

TECHNICAL  PAPER  77.  Report  of  the  Committee  on  Resuscitation  from  Mine 
Gases,  by  W.  B.  Cannon,  G.  W.  Crile,  Joseph  Erlanger,  Yandell  Henderson,  and 
S.  J.  Meltzer.  1914.  36  pp.,  4  figs. 

TECHNICAL  PAPER  92.  Quarry  accidents  in  the  United  States  during  the  calen- 
dar year  1913,  compiled  by  A.  H.  Fay.  1914.  76  pp. 

TECHNICAL  PAPER  94.  Metal-mine  accidents  in  the  United  States  during  the 
calendar  year  1913,  compiled  by  A.  H.  Fay.  1914.  73  pp. 

TECHNICAL  PAPER  100.  Permissible  explosives  tested  prior  to  March  1,  1915, 
by  S.  P.  Howell.  1915.  16  pp. 

TECHNICAL  PAPER  107.  Production  of  explosives  in  the  United  States  during 
the  calendar  year  1914,  by  A.  H.  Fay.  1915.  14  pp. 

TECHNICAL  PAPER  111.  Safety  in  stone  quarrying,  by  O.  P.  Bowles.  1915. 
48  pp.  5  pis.,  4  figs. 

TECHNICAL  PAPER  119.  The  limits  of  inflammability  of  mixtures  of  methane 
and  air,  by  G.  A.  Burrell  and  G.  G.  Oberfell.  1915.  30  pp.,  4  figs. 

MINERS'  CIRCULAR  5.  Electrical  accidents  in  mines,  their  causes  and  preven- 
tion, by  H.  H.  Clark,  W.  D.  Roberts,  L.  C.  Ilsley,  and  H.  F.  Randolph.  1911. 
10  pp.,  3  pis. 

MINERS'  CIRCULAR  7.  Use  and  misuse  of  explosives  in  coal  mining,  by  J.  J. 
Rutledge.  with  a  preface  by  J.  A.  Holmes.  1913.  52  pp.,  8  figs. 

MINERS'  CIRCULAR  8.  First-aid  instructions  for  miners,  by  M.  W.  Glasgow, 
W.  A.  Raudenbush,  and  C.  O.  Roberts.  1913.  67  pp.,  51  figs. 


84  ANALYSIS  OF  PERMISSIBLE  EXPLOSIVES. 

MINERS'  CIRCULAR  11.  Accidents  from  mine  cars  and  locomotives,  by  L.  M. 
Jones.  1912.  16  pp. 

MINERS'  CIRCULAR  12.  The  use  and  care  of  miners'  safety  lamps,  by  J.  W. 
Paul.  1913.  16  pp.,  4  figs. 

MINERS'  CIRCULAR  13.  Safety  in  tunneling,  by  D.  W.  Brunton  and  J.  A.  Davis. 

1913.  19  pp. 

MINERS'  CIRCULAR  14.  Gases  found  in  coal  mines,  by  G.  A.  Burrell  and  F.  M. 
Seibert.  1914.  23  pp. 

MINERS'  CIRCULAR  15.  Rules  for  mine-rescue  and  first-aid  field  contests,  by 
J.  W.  Paul.  1913.  12  pp. 

MINERS'   CIRCULAR  16.  Hints  on   coal-mine  ventilation,   by  J.   J.   Rutledge. 

1914.  22  pp. 

MINERS'  CIRCULAR  17.  Accidents  from  falls  of  rock  or  ore,  by  Edwin  Higgins. 
1914.  15  pp.,  8  figs. 

MINERS'  CIRCULAR  21.  What  a  miner  can  do  to  prevent  gas  and  dust  explo- 
sions, by  G.  S.  Rice.  1914.  24  pp. 


INDEX. 


A.  Page. 
Abel  test  for  stability,  conditions  determin- 
ing        11 

Acetic  acid  as  extractive  agent 49, 50 

Acetone  as  extractive  agent 72,73 

Air,  evaporation  of  ether  by 37,38 

rate  of 39 

Alkali  test  for  detection  of  wheat  flour 16, 17 

Aluminum,  determination  of 56, 70 

Ammonium  alum,  specific  gravity  of 19 

Ammonium  chloride,  specific  gravity  of 19 

See  also  Chlorides. 
Ammonium  nitrate,  moisture  content  of 32 

specific  gravity  of 19 

See  also  Nitrates. 
Ammonium  nitrate  explosives,  detonation  of.         7 

temperature  of  explosion  of 8 

Ammonium  perchlorate,  specific  gravity  of. .       19 

See  also  Perchlorates. 
Ammonium  salts,  determination  of 58, 59 

residue,  drying  of 33,34 

See  also  Ammonium  salts  named. 
Ammonium  sulphate,  specific  gravity  of 19 

See  also  Sulphates. 

Antacids  in  explosives,  purpose  of 67, 68 

Ash  in  corn  meal,  proportion  of 77 

Ash  in  explosives,  determination  of 75 

proportion  of 75 

in  wood  pulp,  proportion  of 77 

Aufhauser,  — ,  cited 76 


B. 


Barium,  determination  of 56 

Barium  nitrate,  specific  gravity  of 19 

See  also  Nitrates. 
Bell-jar  evaporator.    See  Evaporator. 

Berthelot,  M.,  cited 7 

Boiling-point  method  for  determining  molecu- 
lar weight 52 

relative  value  of 53 

Bromoform,  specific  gravity  of 18 

Busch,  M.,  cited 65 

on  determination  of  nitrates 60, 61 

C. 

Calcium,  determination  of 56, 70 

Calcium  carbonate,  specific  gravity  of 19 

Calcium  chloride  as  desiccating  agent 31 

Calcium  silicide,  determination  of 72 

properties  of 72 

Calcium  sulphate,  specific  gravity  of 19 

See  Sulphates. 

Carbohydrates  in  corn  meal,  proportion  of. . .  77 


Page. 

Carbon,  proportion  of,  in  corn  meal 78 

in  wheat  flour 79 

in  wood 76 

in  wood  pulp 77 

Carbon  bisulphide  as  extractive  agent 49, 50, 72 

Carbonates,  determination  of 56 

Castor  oil,  effect  of,  in  determining  nitroglyc- 

erin 43 

solubility  of,  in  nitroglycerin 45 

Cellulose,  view  of 76 

Centrifugal  test  for  exudation.    See  Exuda- 
tion. 

Chevandier ,  — ,  cited 76 

Chlorates,  determination  of 14, 15, 65, 66 

methods  for 62-64 

Chlorides,  determination  of 14, 15, 56, 65, 66 

Chloroform,  specific  gravity  of 18 

Clarke,  F .  W . ,  on  specific  gravities  of  salts ...       19 
Coal-mining  explosives,  essential  properties 

of 6 

Collins,  S.  W.,  on  solubility  of  nitron  nitrate.       61 
Colophony.    See  Rosin. 

Cope,  W .  C.,  acknowledgments  to 5 

Corn  meal,  analyses  of ^ .       78 

composition  of 77 

determination  of 16, 17 

moisture  content  of 32 

view  of 76 

Com  oil,  effect  of,  in  determining  nitroglyc- 
erin   43,44 

solubility  of,  in  nitroglycerin 45 

Corncob  meal,  view  of 78 

' '  Corona  meal . "    See  Corncob  meal . 
Cotton.    See  Cellulose. 
Cottonseed  oil,  effect  of,  in  determining  nitro- 
glycerin   43-44 

solubility  of,  in  nitroglycerin 45 

Crawshaw ,  J .  E . ,  acknowledgments  to 5 

Crucible  holder ,       55 

Crucibles,  for  extraction 55 

D. 

Desiccating  agents.    See  Calcium   chloride; 
sulphuric  acid. 

Desiccation,  determining  moisture  by 22-32 

Desiccators.    See  Vacuum  desiccators. 

Dinitrobenzene,  determination  of. 51 

effect  of,  in  determining  nitroglycerin. ...  43, 44 

Dinitrotoluene,  losses  of,  by  desiccation 25,26 

by  evaporation 40 

solubility  of,  in  nitroglycerin 45, 46 

See  also  "Liquid"  dinitrotoluenes. 
Dynamite,  desiccation  of,  curves  showing. ...  23, 24 
moisture  content  of. 32 

85 


86 


INDEX. 


E. 

Page. 

Engine  oil,  effect  of,  in  determining  nitro- 
glycerin  43,44 

solubility  of,  in  nitroglycerin 45 

Ether  as  extractive  agent 33, 34, 72 

Ether  extract,  analysis  of 37-54 

apparatus  for  evaporating 35, 36 

figure  showing 36 

in  corn  meal,  proportion  of 77 

losses  during  evaporation 37-41 

Evaporator,  bell-jar,  advantage  of 36 

description  of 35, 36 

figure  showing 36 

Explosives,  flame  temperature  of,  reducing  of.         6 

analysis  of,  factors  determining 13 

preparation  of,  for  analysis 12 

sampling  of 12 

water-soluble  ingredients  of,  separation 

of 17-19 

See  also  explosives  named. 

Extraction  with  ether, apparatus  for 34, 35, 36 

method  for 33 

with  hydrochloric  acid,  methods  of 68-72 

with  water  apparatus  for 55 

method  for 54,55 

E  xtractive  agents.    See  Acetic  acid ;  Acetone ; 
Carbon  bisulphide;  Ether;  Hydro- 
chloric acid;  Water. 
Exudation  of  nitroglycerin,  test  for 10 

F. 

Fiber,  crude,  in  corn  meal,  proportion  of 77 

Fieldner,  A.  C.,  analyses  of  wheat  flour  by. .  79 
"  Filtering  crucible  holder,"  for  extraction. . .  55 
Flame  of  explosive,  temperature  of,  methods 

of  reducing 6 

Formaldehyde,  determination  of  chlorates  by  63, 64 

1 '  Formalin. "    See  Formaldehyde. 

Fusion  method  for  determination  of  perchlo- 

rates 64,65 

Glycerin  test  for  detection  of  corn  meal 16 

G. 

Gody,  L.,  cited 63 

Gottlieb,  — ,  cited 76 

Gravimetric  density  of  explosive,  determina- 
tion of. 10 

Griitzner,  B.,  determination  of  chlorate  by. .  63 

Gum  arabic  hi  explosives,  determination  of. .  15, 67 

purpose  of 67 

H. 

Hopkins,  — ,  cited 78 

Hunter,  J.  H. ,  acknowledgments  to 5 

Hyde,  A.  L.,  acknowledgments  to 5 

evaporator  devised  by 35 

on  boiling-point  method  for  determining 

molecular  weight 52 

on   determination   of   nitrosubstitution 

compounds 47 

Hydrated  explosives,  constituents  of 8, 9 

8 

.  67,68 
78 
79 
76 
77 


definition  of 

Hydrochloric  acid  as  extractive  agent. 
Hydrogen,  proportion  of  in  corn  meal. 

in  wheat  flour 

in  wood 

in  wood  pulp 


I. 

Page. 
Infusorial  earth,  views  of  ....................       74 

"International"  75°  test  for  stability,  descrip- 

tion of  .............................  1  1,  12 

Iron,  determination  o  ........................       7Q 

K. 

Kieselguhr.    See  Infusorial  earth. 

Konig,  —  ,  cited  ..............................       73 

L. 

Le  Roy,  G.  A.,  test  devised  by  ..............       16 

Lheure,  —  ,  tests  of  ...........................        7 

"  Liquid  "  dinitrotoluenes,  definition  of  ......       24 

losses  of,  by  desiccation  ...................  25,27 

curve  showing  ...................       28 

factors  affecting  ..................  25,26 

by  evaporation  of  ether  ..............       40 

See  also  Dinitrotoluenes. 
"Liquid"  nitrotoluene,  determination  of  ____       50 

See  also  "Liquid"  dinitrotoluene;  "Liq- 

uid" trinitrotoluene. 
"  Liquid"  trinitrotoluenes,  definition  of  ......       24 

losses  of,  by  desiccation  ..................  25,27 

curve  showing  ...................       28 

factors  affecting  ..................  25,26 

by  evaporation  of  ether  ..............       40 

See  also  Trinitrotoluenes. 
Lobry  de  Bruyn,  C.  A.,  tests  of  ..............         7 

Low-flame  explosives,  components  of,  list  of.  .       13 

M. 

Magnesium,  determination  of  ................  56,  70 

Magnesium  carbonate,  specific  gravity  of  ____       19 

Magnesium  sulphate,  desiccation  of,  losses  in.       31 

specific  gravity  of  ........................       19 

tests  with  ...............................  30,  31 

Manganese  dioxide,  determination  of  ........        71 

specific  gravity  of  ........................       19 

Microscopes  for  examining  residue,  types  of.  . 
Microscopic  examination  of  residue.    See  Res- 

idue. 
Moisture  in  corn  meal,  proportion  of  .........        77 

in  explosives,  determination  of  ..........  21,  32 

factors  affecting  ..................  22-32 

in  wood  pulp,  proportion  of  ..............        77 

Mononitrobenzene,  determination  of  .........       51 

effect  of,  in  determining  moisture  ........  29,  30 

in  determining  nitroglycerin  .........  43,  44 

JMononitronaphthalene,  determination  of  ____  14,51 

effect  of,  in  determining  nitroglycerin  ____  43,  44 

solubility  of,  in  nitroglycerin  ............  45,  46 

Mononitro  toluene,  losses  of,  by  desiccation...  25-27 
factors  affecting  .................  25,  26 

by  evaporation  of  ether  ..............       40 

effect  of,  in  determining  moisture  ........       29 

solubility  of,  in  nitroglycerin  ............  45,  46 

Muck,—  ,  cited  ..............................       76 


" 


N. 

Nitrates,  determination  of  ................  60-62,  66 

See  also  Nitrates  named. 
Nitrocellulose,  determination  of  ...........  15,  72,  73 

view  of  ..................................        76 

Nitro  compound.    See  Compounds  named. 


INDEX. 


87 


Page. 

Nitropen,  determination  of 51, 52 

proportion  of,  in  corn  meal 78 

in  wheat  flour 79 

Nitroglycerin,  determination  of,  factors  af- 
fecting   41-45 

loss  of,  by  desiccation 22 

curves  showing 23, 24 

effect  of  temperature  on 22, 23 

in  evaporator 37, 38 

factors  affecting 39 

moisture  content  of 32 

relative  solubility  of 53 

Nitroglycerin  explosives,  constituents  of 9 

definition  of .' 9 

moisture  in 21 

Nitrometer  method,  determining  nitrates  by.       60 

Nitron,  recovery  of,  method  for 62 

Nitron  method,  determining  nitrates  by 60-62 

determining  perchlorates  by 65 

Nitropolyglycerin,  determination  01 14, 51, 53 

relative  solubility  of 53 

Nitrostarch,  use  of,  as  explosive 9 

determination  of 15,72,73 

Nitrosubstitution  compounds,  determination 

of 47-50 

apparatus  for 47-49 

figure  showing 48 

factors  affecting 47 

See  also  Compounds  named. 
Nitrotoluenes,   volatility   of,   factors  affect- 
ing  24,25,39-41 

See  also  Dinitro toluene;    Mononitrotolu- 
ene;  Trinitrotoluene. 


O. 


46 


Oils  in  ether  extract,  determination  of 

See  also  Oils  named. 

Organic  nitrate  explosives,  definition  of 9 

Ormsby ,  H.  P.,  analyses  of  corn  meal  by 78 

Orthomononitrotoluene.     See    Mononitroto- 

luene. 
Orthonitrotoluene.    See  Mononitro toluene. 

Oxalates,  determination  of 56 

Oxygen,  proportion  of,  in  corn  meal 78 

in  wheat  fiour 79 

in  wood 76 

in  wood  pulp 77 

P. 

Paraffin,  determination  of 46 

effect  of,  in  determining  nitroglycerin 43, 44 

solubility  of,  in  nitroglycerin 45 

Paramononitrotoluene.  See  Mononitro  toluene. 

Peanut-shell  meal,  view  of 78 

Perchlorate  method  for  determining  potas- 
sium   59,60 

Perchlorates,  determination  of 14, 15, 64-66 

Permissible  explosives,  analysis  of,  methods 

for 14,20,21 

chemical  examination  of,  purpose  of 5 

classification  of 6, 7 

definition  of 5 

requirements  of 10 

See  also  Explosives;  and  permissible  ex- 
plosives named. 


Page. 

Poole,  H.,  cited 76 

Potassium,  determination  of 56,59,60 

Potassium  alum,  desiccation  of,  loss  of  weight 

in 30,31 

specific  gravity  of 19 

Potassium  chlorate,  specific  gravity  of 19 

See  also  Chlorates. 
Potassium  chloride,  specific  gravity  of 19 

See  also  Chlorides. 
Potassium  nitrate,  specific  gravity  of 19 

See  also  Nitrates. 
Potassium  perchlorate,  specific  gravity  of. ...       19 

See  also  Perchlorates. 

Potassium  sulphate,  specific  gravity  of 19 

Proteids  in  corn  meal,  proportion  of 77 

Q. 
Quarrying,  explosives  for,  essent  ial  factor  In . .        6 

R. 

Residue,  insoluble,  method  of  drying 55, 56 

conditions  determining 33, 34 

microscopic  examination  of 20, 74 

treatment  of 57, 58 

Resin,  determination  of 47 

solubility  of,  in  nitroglycerin 45, 46 

Retgers,  — ,  on  specific  gravities  of  salts 19 

Rice  hulls,  view  of 78 

Rose,  G.,  on  specific  gravities  of  salts 19 

Rosin,  effect  of,  in  determining  nitroglycerin.  43, 44 

solubility  of,  in  nitroglycerin 45, 46 


Sampling  explosives,  method  for 12 

Sawdust,  view  of 74 

Schroder,  — ,  on  specific  gravities  of  salts 19 

Screening  separation  of  solid  ingredients  by.  17,18 

Sensitizers  for  ammonium  nitrate 8 

Se*rullas,  — ,  determination  of  potassium  by . .       59 
Sodium  chloride,  specific  gravity  of 19 

See  also  Chlorides. 
Sodium  nitrate,  moisture  content  of 32 

specific  gravity  of 19 

See  also  Nitrates. 

Sodium  sulphate,  specific  gravity  of 19 

Specific  gravity  separation  of  solid  ingredients .  18-20 

Stability  of  explosives,  tests  for 11, 12 

Starch  in  explosives,  determination  of 68, 69 

Stieg,  F .  B . ,  modified  tube  devised  by 34 

Sugar,  determination  of,  method  for 66 

Sulphates,  determination  of 56 

Sulphur,  determination  of 46, 72 

solubility  of,  in  nitroglycerin 45 

Sulphur  dioxide,  determination  of  chlorate  by  62, 63 

Sulphuric  acid  as  desiccating  agent 21, 

25,26,28,29,31 
T. 

Taylor,  C .  A . ,  acknowledgments  to 6 

Tolerances  for  analyses 80 

Trinitrotoluene,  loss  of,  by  desiccation 25, 26 

by  evaporation  of  ether 40 

solubility  of,  in  nitroglycerin 45, 46 

Tunneling,  explosives  for,  properties  of 6 

Tutton,  — ,  on  specific  gravities  of  salts 19 


88 


INDEX. 


V. 

Vacuum  desiccators,  use  of 26, 27 

Vaseline,  determination  of 46 

effect  of,  in  determining  nitroglycerin 42, 44 

solubility  of,  in  nitroglycerin 45 

Vegetable-ivory  meal,  view  of 78 


Water  as  extractive  agent 54, 55, 57 

Water  in  explosives,  determination  of 31 

See  also  Moisture. 

Water  extract,  constituents  of,  determina- 
tion of 56-67 

Water  of  crystallization,  effect  of,  in  moisture 

determination 30-31 

Wheat  flour,  composition  of 78, 79 

in  explosives,  tests  for 16, 17 


Page. 

Wheat  flour,  moisture  content  of 32 

views  of 74, 76 

Wiley  extraction  apparatus,  tube  for 34, 35 

figure  showing 35 

method  of  using 35 

Wood  pulp  in  explosives,  analyses  of 77 

test  for 16 

moisture  content  of 32 

solubility  of,  in  hydrochloric  acid 69 

view  of 74,76 

Woods,  analyses  of 76 

Woult,  — ,  on  specific  gravities  of  salts 19 

Z. 
Zinc,  determination  of 56, 58,59, 7 


O 


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